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LABORATORY MANUAL OF 
AGRICULTURAL CHEMISTRY 

HEDGES AND BRYANT 












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PROFESSOK S. W. JOHNSON 



LABORATORY MANUAL OF 
AGRICULTURAL CHEMISTRY 



BY 



CHARLES CLEVELAND HEDGES, Ph.D. 

PROFESSOR OF AGRICULTURAL CHEMISTRY AND HEAD OF THE 

DEPARTMENT OF CHEMISTRY AND CHE3IICAL ENGINEERING 

TEXAS AGRICULTURAL AND MECHANICAL COLLEGE 



AND 



WILLIAM THOREAU BRYANT, B.S., Ch.E. 

INSTRUCTOR IN AGRICULTURAL CHEMISTRY 
TEXAS AGRICULTURAL AND MECHANICAL COLLEGE 



GINN AND COMPANY 

BOSTON • NEW YORK • CHICAGO • LONDON 
ATLANTA • DALLAS • COLUMBUS • SAN FRANCISCO 






COPYRIGHT, 1916, BY 

CHARLES CLEVELAND HEDGES AND 
WILLIAM THOREAU BRYANT 



ALL RIGHTS RESERVED 
516.8 




GINN AND COMPANY • PRO- 
PRIETORS • BOSTON • U.S.A. 



©CI,A438;i74 



PREFACE 

This Laboratory Manual is the outgrowth of several 
years' experience in agricultural institutions in teaching 
chemistry in its various relations to agriculture. The direc- 
tions are designed as a laboratory guide for students in 
agricultural chemistry. It is necessary that this course be 
preceded by a course in general or inorganic chemistry 
and accompanied by a course in the theory of agricultural 
chemistry. A course in quantitative analysis is not neces- 
sarily a prerequisite. At the beginning of the Manual, along 
with the preparation of standard solutions used later in 
the analysis of agricultural products, a few experiments 
in quantitative analysis have been given to illustrate the 
fundamental principles and more important methods of 
manipulation. Directions as to the setting up of apparatus, 
details of manipulation, use and care of the balance, chem- 
istry, and stoichiometry should be given in lectures accom- 
panying the laboratory practice. The authors did not 
consider it advisable to burden the laboratory guide with 
a large amount of explanatory notes giving reasons for 
each step in the directions. It was thought that this could 
be accomplished to better advantage by means of lectures 
accompanying the laboratory work, and by questions at 
the end of each experiment that are designed to encourage 
the student to think for himself and to do outside reading. 
This arrangement gives the teacher an opportunity to 

[V] 



present the theory in any particular manner he may desire 
and to come in closer contact with the students, thereby 
making the practice more interesting to them by the personal 
contact. The directions for each experiment are simplified, 
as far as it is considered advisable, in order that the student 
might be able to pursue the laboratory work with the least 
possible assistance from the teacher. In the Appendix is 
given a list of some of the most important works bearing 
on this subject so as to further the interest of the student 
by encouraging outside reading. 

In preparing this Manual free use has been made of 
standard works on quantitative analysis, of the publica- 
tions of the Association of Official Agricultural Chemists, 
and of the bulletins of the Bureau of Chemistry, United 
States Department of Agriculture. The authors desire to 
acknowledge their obligation to the " Letter-Files " and to 
the Yale University Press for the portrait of Professor 
S. W. Johnson used as the frontispiece. 

C. C. HEDGES 
College Station, Texas W. T. BRYANT 



[vi] 



CONTENTS 



PART I. PREPARATORY QUANTITATIVE ANALYSIS 

Experiment page 

Introduction 1 

1. Preparation of Cleaning Mixture 2 

2. Preparation of an Approximate N/10 NaOH Solution . . 3 

3. Preparation of an Approximate N/5 HCl Solution ... 3 

4. Determination of Equivalent Volumes 4 

5. I. Preparation of a Perforated or Goocli Crucible ... 6 
II. Standardization of HCl Solution by Gravimetric Method 8 

6. I. Standardization of the HCl Solution by Volumetric 

Method 10 

II. Calculation of the Titre of the NaOH Solution ... 12 

7. Determination of the Strength of an Unknown Alkali 

Solution 12 

8. Determination of the Strength of an Unknown Acid Solution 13 

9. Determination of the Strength of an Unknown KgCOg Solu- 

tion, using Methyl Orange as Indicator 13 

10. Determination of the Strength of an Unknown 1^2^03 Solu- 

tion, using Phenolphthalein as Indicator 13 

11. Determination of the Strength of an Unknown NaOH and 

Na^COg Solution 14 

12. Determination of Acetic Acid in Vinegar 15 

13. Determination of Total Solids in Vinegar , 16 

14. Determination of Ash in Vinegar 16 

15. Preparation of Standard Potassium Permanganate Solution 

(KMnO^) 17 

16. Determination of the Amount of Calcium Oxide in Limestone 18 



[vii] 



PART II. ANALYSIS OF FEEDSTUFFS 

EXPERIMENT PAGE 

Preparation of a Sample of Feedstuff for Analysis ... 21 

17. Determination of Moisture in Feedstuffs 21 

18. Determination of Ash in Feedstuffs 22 

19. Determination of Crude Protein in Feedstuffs .... 23 

20. Determination of Ether Extract (Fat) in Feedstuffs . . 26 

21. Preparation of a 1.25 Per Cent HgSO^ Solution and a 1.25 

Per Cent NaOH Solution 28 

22. Determination of Crude Fiber in Feedstuffs 29 

23. Determination of Nitrogen-Free Extract in Feedstuffs . . 30 

PART III. CHEMICAL ANALYSIS OF SOIL 

Directions for taking a Sample of Soil for Analysis ... 32 

Preparation of Samples for Analysis 33 

24. Qualitative Analysis of Soil 34 

25. Determination of Moisture in Soil 35 

26. Determination of Volatile Matter in Soil 36 

27. Determination of Humus in Soil 36 

28. Determination of Nitrogen in Soil (Nitrates Absent) . . 37 

29. Test for Acidity or Alkalinity of Soil and Determination of 

Lime Requirements 38 

30. Strong Hydrochloric Acid (sp. gr. 1.115) Digestion of Soil. 

Preparation of Soil Solution 39 

31. Determination of Iron (Fe) in Soil Solution by Volumetric 

Method 41 

32. Determination of Calcium (Ca) in Soil Solution by Volu- 

metric Method 42 

33. Determination of Phosphoric Acid (P2^5) ^^ ^^^^ Solution 

by Gravimetric Method 43 

33 a. Determination of Phosphoric Acid (Pa^s) ^^ Soil Solution 

by Volumetric Method (Optional Method) .... 45 

34. Determination of Potash (KgO) in Soil Solution by the 

Use of Platinum Solution 47 

34 a. Determination of Potash (KgO) in Soil Solution by 

Volumetric Method (Optional Method) 49 

34 h. Determination of Potash (K2O) in Soil Solution by the 
Use of Platinum Solution (Moore's Method modified) 
(Optional Method) 52 

[ viii ] 



PART IV. ANALYSIS OF FERTILIZERS 

EXPERIMENT PAGE 

Preparation of Sample of Fertilizer for Analysis .... 55 

35. Determination of Moisture in Fertilizer 55 

36. Preparation of a Standard NaOH Solution for Phosphoric 

Acid (P2^5) Determination 56 

37. Determination of Total Phosphoric Acid (PgOg) in Fertilizer 57 

38. Determination of Water-Soluble Phosphoric Acid (Pg^s) i^ 

Fertilizer 59 

39. Determination of Citrate-Soluble Phosphoric Acid (P0O5) 

in Fertilizer 59 

40. Determination of Potash (K2O) in a Mixed Fertilizer by 

the use of Platinum Solution 61 

40 a. Determination of Potash (K2O) in a Mixed Fertilizer by 

Volumetric Method (Optional Method) 62 

41. Determination of Nitrogen in Fertilizers (Nitrates Present) 63 

PART V. ANALYSIS OF INSECTICIDE AND FUNGICIDE 

42. Preparation and Standardization of Solution for Determi- 

nation of Arsenious Oxide (AsgOg) in Paris Green . 64 

43. Determination of Total Arsenious Oxide (AsgOg) in Paris 

Green 65 

44. Determination of Water-Soluble Arsenious Oxide (AS2O3) 

in Paris Green 66 

45. Determination of Moisture in Lead Arsenate 67 

46. Determination of Total Lead Oxide in Lead Arsenate . . 67 

47. Determination of AVater-Soluble Lead Oxide in Lead 

Arsenate 68 

48. Determination of Total Arsenic Oxide (AS2O5) in Lead 

Arsenate 69 

49. Determination of Water-Soluble Arsenic Oxide (AS2O5) in 

Lead Arsenate 70 

50. Testing Bordeaux Mixture for Soluble Copper 70 

PART VI. ANALYSIS OF MILK 

51. Determination of Specific Gravity of Milk 72 

52. Determination of Total Solids in Milk 73 

53. Determination of Ash in Milk 73 

[ix] 



EXPERIMENT PAGE 

54. Determination of Fat in Milk by the Werner-Schmidt 

Method 74 

55. Determination of Total Protein (Casein and Albumin) in 

Milk 75 

56. Determination of Casein in Milk 75 

PART VII. A BRIEF SANITARY EXAMINATION OF WATER 

57. Determination of Total Solids in Water 77 

58. Determination of Chlorine as Chlorides in Water .... 77 

59. Detection of Free Ammonia in Water 78 

60. Detection of Nitrites in Water 79 

61. Detection of Nitrates in Water 79 

62. Determination of Absorbed Oxygen in Water 80 

63. Determination of Temporary Hardness or Alkalinity of 

Water 80 

PART VIII. APPENDIX 

Books of Reference 82 

Tables of Weights 83 

Tables of Measm-es 84 

Strength of HCl Solution at Different Densities, 15° C. . . . 85 

Strength of H2SO4 Solution at Different Densities, 15° C. . . 80 

Strength of HNO3 Solution at Different Densities, 15° C. . . 86 

Strength of NH^OH Solution at Different Densities, 15° C. . . 86 

Strength of NaOH Solution at Different Densities, 15° C. . . 87 

Rules to determine Solubilities in Water 88 

Directions for Preparation of Reagents 88 

Apparatus for Desk Equipment 93 

International Atomic Weights (1916) 94 



[^] 



LABORATORY MANUAL OF 
AGRICULTURAL CHEMISTRY 



LABORATORY MANUAL OF 
AGRICULTURAL CHEMISTRY 

PART I 

PREPARATORY QUANTITATIVE ANALYSIS 
Introduction 

At the first laboratory period the student should check 
up the apparatus in the desk assigned to him and imme- 
diately report any shortage or broken apparatus to the 
instructor in charge. Each student should be required to 
turn in at the end of the term's work a desk fully equipped 
with a complete set of apparatus in perfect condition. He 
should also be required to make a wash bottle to be used 
m the analytical work, and have it inspected by the in- 
structor. All records of the laboratory work should be 
recorded in a notebook in a neat and systematic manner. 

Reports of experiments and answers to all questions 
should be submitted at the next period, after the experi- 
ment is completed. Cleanliness, neatness, patience, and the 
most careful attention to details of the directions cannot 
be overemphasized in laboratory manipulations. 



[1] 



Experiment No. 1 

PREPARATION OF CLEANING MIXTURE 

Dissolve 20 g. of commercial KJ^vfi^ in 75 cc. of warm 
water, cool, and pour slowly into it, with constant stirring, 
115 cc. of commercial sulphuric acid (H^SO^). The potas- 
sium dichromate solution should be placed in a No. 7 evap- 
orating dish, if convenient, before pouring the sulphuric 
acid into it. When the solution is completely cooled, it 
should be transferred to a 250 cc. wide-mouthed bottle. 
(Be careful in making this mixture, so as not to spill it 
on your clothes.) Invert the burettes in the cleaning mix- 
ture, attach the rubber tubing, draw up to the 50 cc. mark, 
and allow to stand for at least half an hour before being 
used. (^See that the burette stopcocks work smoothly and are not 
clogged ivith grease.) Coat the burette stopcocks with a very 
small amount of vaseline to prevent sticking. The cleaning 
mixture is to be used throughout the course. Avoid the 
addition of water to the cleaning mixture. A burette is 
clean when the drops of water will not adhere to the sides. 
Other useful cleaning mixtures are soap solutions, alcoholic 
KOH solutions, and ammoniacal alcohol solutions. 

Chemistry 

K,Crp^ + 2 H^SO^ = 2 KHSO^ + H^Cr^^. 

H^Cr^^ breaks up into H^CrO^ + Cr03 (red ppt). 

2 H^CrO^ = Cr^O^ + 2 Hp + 3 O. 

2Cr03 = CrP3 + 3 0. 

Both H^CrO^ and CrO^ oxidize organic matter. 

Ci-p^ + 8 H^SO, = Cr, (SO,)3 + 3 H^O. 

[2] 



Questions 

1. AVhy does cleaning mixture clean ? 2. Write equation. 
3. What would you use to clean grease from glassware ? Give 
reason. 4. After using the mixture for some time, it may 
become green in color. Give reason. 5. What is meant by 
the terms comfimercial and C. P. cheynicals ? 



Experiment No. 2 

PREPARATION OF AN APPROXIMATE N/10 NaOH SOLUTION 

A normal solution is one which contains the hydrogen 
equivalent of the active constituent in grams per liter ; that 
is, the amount in a liter which brings into reaction 1.008 g. 
of hydrogen or 8 g. of oxygen, or their equivalent. 

One molecule of NaOH brings into reaction one atom 
of hydrogen when it reacts with an acid. Therefore 
40.058 g. of NaOH is equivalent to 1.008 g. of hydrogen ; 
hence there are 40.058 g. of NaOH in one liter of normal 
NaOH solution, and 4.0058 g. in one liter of a N/10 
NaOH solution. 

Since the NaOH "sticks" contain about 10 to 20 per 
cent of water, weigh out (on rough balance) 5 g., dissolve 
in distilled water, and dilute to one liter. Shake the 
solution thoroughly. 

Experiment No. 3 

PREPARATION OF AN APPROXIMATE N/6 HCl SOLUTION 

One molecule of hydrochloric acid (HCl) contains one 
replaceable hydrogen atom; therefore 36.458 g. of hydrogen 
chloride furnishes 1.008 g. of reacting hydrogen. In other 
words, the molecular weight of HCl (36.458) contains 

[3] 



1.008 parts of reacting or replaceable hydrogen. Therefore 
it requires 36.458 g. of hydrogen chloride (HCl) for one 
liter of a normal hydrochloric acid (HCl) solution, and 
7.2916 g. for one liter of a N/5 hydrochloric acid (HCl) 
solution. 

The specific gravity of the C. P. concentrated hydro- 
chloric acid solution on the reagent shelf should be 
determined by means of a specific-gravity spindle or 
hydrometer. 

Example. Should the specific gravity of the C. P. concentrated 

hydrochloric acid solution on the reagent shelf be 1.175, it would 

contain 34.43 per cent of hydrogen chloride by M-eight (see table 

of specific gravities, p. 85). Therefore 1.175 times .3443 = grams of 

hydrogen chloride in 1 cc. of the C. P. concentrated hydrochloric 

7 '^916 
acid solution, and ^ ^^J" — — -— = 18 cc. of C. P. concentrated hydro- 
1.17o X .3443 ^ 

chloric acid required to furnish approximately 7.2916 g. of hydro- 
gen chloride. This is the weight or amount of hydrogen chloride 
required for one liter of a N/5 hydrochloric acid solution, providing 
the concentrated acid is of the above specific gravity. 

Measure out the amount of the concentrated C. P. hy- 
drochloric acid required by your calculations (in the above 
example it would be 18 cc.) and dilute to one liter with 
distilled water. Shake the solution thoroughly before 
usmg. 

Experiment No. 4 

DETERMINATION OF EQUIVALENT VOLUMES 

Rinse out two burettes (which have been standing in 
cleaning mixture) with distilled water. After each burette 
is rinsed with distilled water, it should be rinsed again 
with a 5 cc. portion of the solution to be used in the 
respective burette, so as to remove any adhering particles 

[4] 



of water (letting the solution run through the tip each 
time). Label the burette according to the solution to be 
used therein. Fill one of the burettes * a little above the 
zero mark with the approximate N/10 NaOH solution. 
Open the stopcock or pinchcock cautiously until the read- 
ing of solution in the burette is zero. In the same manner 
fill the other burette with the approximate N/5 HCl solu- 
tion, using the same care as to washing, etc. Draw out 
approximately 10 cc. of the NaOH solution into a 250 cc. 
Erlenmeyer flask or beaker. Dilute to 50 cc. with distilled 
water, add one drop of methyl orange, and then rapidly 
add the HCl solution until the solution in the flask or 
beaker changes color, indicating an acid solution. Now 
bring the flask or beaker under the burette containing the 
NaOH, and add the NaOH solution more slowly, until the 
color turns yellow. Then bring the flask or beaker under 
the burette containing the HCl, and add the HCl solution 
slowly until the solution turns red. Continue this opera- 
tion until a point is obtained where one drop, or even 
half a drop, of either solution will cause a color change. 
When this point — known as the end-point — is reached, 
allow the solutions in the burettes to dram for a minute, 
and then read the exact volume of each solution used. 

Record in your laboratory notebook the exact volume of 
solution used. As a check on this determination and also 
as work with indicators, make titrations, using phenol- 
phthalein, cochineal, and methyl red as indicators. Make 
at least two titrations with each indicator. Different 
determinations should agree within .05 cc. Take the aver- 
age of the titration for the calculations. From the data 

* It is advisable to use a rubber-tipped burette for the alkali 
solution. 

[5] 



obtained calculate and report the cubic centimeters of 
HCl solution neutralized by 1 cc. of the NaOH solution. 
Also calculate and report the cubic centimeters of NaOH 
solution neutralized by 1 cc. of the HCl solution. 

Questions 

1. How many grams of the following reagents will be 
required for one liter of a normal solution ; one liter of 
fifth-normal solution : HNO3, H,SO^, HgPO^, H.^C^O^, 2 H^O, 
NH^H, NaHCOg, AgN03, K,SO^ ? 2. How many cubic cen- 
timeters (cc.) of N/10 HCl = 15cc. of N/1 NHpH? N/5 
K2CO3? N/10 NaOH? N/1 KOH=:10cc.? N/4 H.C.p^? N/2 
H.^SO^? 3. If 8g. of a sample containing some NaOH were 
dissolved in 200 cc. of distilled water, and 20 cc. of this solu- 
tion were equivalent to 15 cc. of a N/5 acid, what would be 
the percentage of NaOH in the original material ? 

Experiment No. 5 

I. PREPARATION OF A PERFORATED OR GOOCH CRUCIBLE 

Prepare two crucibles in the following manner: Place 
the Gooch funnel in the neck of a filter flask by means 
of the rubber stopper, stretch the rubber band over the 
funnel, and place the crucible in the opening. Con- 
nect the filter flask, by means of a rubber tubing, to 
the filter pump, and before turning on the suction pour 
into the crucible some of the coarse, suspended asbestos* 
(obtained by shaking the bottle). When the water has 
filtered through, turn on the suction and pour on some of 
the finer asbestos (supernatant liquid obtained on allow- 
ing the solution to settle a short time). Tap well with 
flattened glass rod, and add another layer. Then wash 

* Prepared according to directions on page 88. 

[6] 



with at least 100 cc. of distilled water, and dry in the air 
bath at 130°-150° C. for two hours. Cool m desiccator, and 
weigh accurately to tenths of a milligram. (Crucibles 




ANALYTICAL BALANCE 



should be handled only with clean forceps.) The asbestos 
film should be thin enough to be translucent when wet, 
but not so thin that it will be liable to permit a fine 
precipitate to pass through. 

[7] 



Do not put any labels on the crucibles, and do not mark 
them. They may be identified by placing them in a labeled 
funnel.* The crucibles should be treated in the same way 
before and after receivmg the precipitates. This applies 
to the length of time in the drying oven, the heat applied, 
and the length of time they stand in the desiccator before 
weighmg. 

Questions 

1. What is asbestos, and how is it obtained ? 2. How should 
asbestos be prepared for use in a Gooch crucible ? 3. In 
Experiment No. 5, why not filter through a filter paper? 
4. Give three precautions that should be taken when using a 
desiccator. 5. Name four reagents that could be used in a 
desiccator, for drying purposes, and discuss their efficiency. 

II. STANDARDIZATION OF HCl SOLUTION BY GKAVIMETRIC 

METHOD 

Into two 250 cc. Erlenmeyer flasks, which have been 
cleaned with cleaning mixture and carefully rinsed with 
distilled water, measure out accurately from a burette 
25 cc. portions of HCl solution. (Allow the burette to 
drain for about five minutes before reading.) Add 75 cc. 
of distilled water, 5 cc. of C. P. cencentrated HNO^ solu- 
tion, and then a solution of silver nitrate t (AgNOg) 
very gradually and with constant agitation of solution 
until the precipitation is complete. Close the flask with 
a clean rubber stopper, wrap in a black cloth, and shake 
the flask vigorously for several minutes until the AgCl 

* Crucibles may be permanently marked for identification either with 
China paints by Yoder's method (circular of Bureau of Chemistry) or, 
more conveniently, by burning in a '^ grease " Prussian blue pencil mark. 
J. E. Huber, Chemist Analyst, January, 1915, p. 25. 

i Prepared according to directions on page 89. 

[8] 



is flocculated and the supernatant liquid is perfectly clear. 
When the precipitation is complete, the supernatant liquid 
quickly becomes clear. To this clear portion a drop of 
silver nitrate may be added to decide whether enough 
has been added for complete precipitation of the hydro- 
chloric acid. Avoid the addition of an excess of the 
silver solution. It is necessary to protect the flask con- 
taining the precipitate from the light, as much as possible, 
as light tends to decompose the silver chloride precipitate 
(AgCl). 

Let the precipitate settle, then filter off the supernatant 
liquid through the tared Gooch crucible by suction, intro- 
ducing as little of the precipitate as possible on the filter. 
Wash with about 150 cc. of a cold 1 per cent HNO^ solution 
by similar decantation through the Gooch. Transfer the 
precipitate, without loss, from the flask to the tared cruci- 
ble, with about 100 cc. more of a 1 per cent HNO^ solu- 
tion, making sure that none is left in the flask or on the 
rubber stopper, and wash thoroughly with a 1 per cent 
HNOg solution until 15 cc. of the filtrate does not give 
a test for silver nitrate (AgNO^). Suck fairly dry. Dry 
the crucible and contents for two hours at 130°-150° C, 
cool in desiccator, and weigh. Heat again for one hour, 
cool, and reweigh. Repeat until weight is constant. 
Duplicates must not differ in weight more than 1 mg. 
At least four trials should be made. 

Chemistry 

AgNOg + HCl = AgCl -h HNO3 

Mol. wt. of AgCl : mol. wt. of HCl : : weight of ppt. : x 
X = grams of hydrogen chloride (HCl) in number of 
cubic centimeters of hydrochloric acid solution used. 

[9] 



= p-rams of hydrog^en chloride 

Volume of HCl used "" ^ ^ 

(HCl) in 1 cc. of the hydrochloric acid solution, which is 

known as the titre of that solution. 

Questions 

1. Show how to make a N/10 HCl solution, a N/5 H^SO^ 
solution, a N/10 HNO3 solution, a N/20 NaOH solution, 
using HCl, sp. gr. 1.185 ; H^SO^, sp. gr. 1.8 ; HNO3, sp. gr. 
1.4 ; NaOH, containing 20 per cent of water. 2. What is the 
percentage of Ag in AgCl ? Fe in FeS0^(NHj2S0^ • 6Hp? 
S in BaSO^ ? and CaO in CaCOg ? 3. How many cubic centi- 
meters of HCl (sp. gr. 1.2) are necessary to precipitate com- 
pletely the silver in 2 g. of AgNO^ ? 4. How many cubic 
centimeters of N/10 AgNOg solution will be necessary to 
precipitate the chlorine from .12 g. of CaCl^ ? 5. What effect 
has light upon AgCl ? Explain. 

Experiment No. 6 

I. STANDARDIZATION OF THE HCl SOLUTION BY VOLU- 
METRIC METHOD 

Weigh out accurately 0.2 to 0.3 g. portions of C. P. 
Na^COg into 250 cc. Erlenmeyer flasks or beakers, and 
dissolve each portion in 50 cc. of distilled water. Add 
one drop of methyl orange to one portion, and titrate with 
HCl solution until the first tmge of pink appears. Repeat 
the operation with the second portion. Record accurately 
the burette readings. 

Chemistry and Calculations 

Na^Og + 2 HCl = 2 NaCl + Hp -f CO, 

Mol. wt. of Na^COg : mol. wt. of 2 HCl : : wt. of Na^Og : x 

106.1 : 72.916 : : weight of Na^CO^ taken : x 

[10] 



— = grams of hydrogen chloride 

Volume of HCl used 

(HCl) in 1 cc. of the hydrochloric acid solution, which is 

known as the titre of that solution. If the duplicates 




APPARATUS FOR QUANTITATIVE ANALYSIS 

i, Erlenmeyer flask (500 cc.) ; ^, wash bottle ; 5, measuring flasks (500 
and 1000 cc.) ; 4, burettes and burette holder ; 5, desiccator ; <?, grad- 
uated cylinder (50 cc.) ; 7, indicator bottles ; 5, specific-gravity hydrom- 
eter and cylinder ; 9, porcelain evaporating dish ; 10^ porcelain crucible 
and cover ; ii, pipette (25 cc.) 

do not agree to within 0.05 mg., the work must be re- 
peated until the duplicates do agree. The results of 
this experiment should check with those obtained in 
Experiment No. 5. Report the titre of the HCl solution 
as obtained in the two experiments. 

[11] 



11. CALCULATION OF THE TITRE OF THE NaOH SOLUTION 

By the use of the titre of the hydrochloric acid solu- 
tion determined in Experiment No. 5 and the volume of 
hydrochloric acid solution neutralized by 1 cc. of the NaOH 
solution, as determined from the equivalent volume work 
(Exp. No. 4), calculate the titre of the NaOH solution. 

Chemistry 

NaOH + HCl = NaCl + H^ 

40.008 : 36.458 ::x'. (titre of HCl solution) times (the 
cubic centimeters of HCl neutralized by 1 cc. of the 
NaOH). 

a; = grams of NaOH in 1 cc. of the NaOH solution, 
which is known as the titre of that solution. 

Questions 

1. Define a normal solution, a standard solution, and a 
per cent solution. 2. Give difference between N/1 HCl and 
1 per cent HCl solution. 3. G-ive the titre of the following 
solutions: 1.25 per cent NaOH; 1.25 per cent H^SO^; 4 per 
cent NH^OH. 4. What is the difference, if any, between 
a 5 per cent NaOH and a N/5 NaOH solution ? 

Experiment No. 7 

DETEEMINATION OF THE STRENGTH OF AN UNKNOWN 
ALKALI SOLUTION 

After cleaning a burette and rinsing with a 5 cc. portion 
of the unknown solution, fill it to the zero mark, accord- 
ing to directions in Experiment No. 4. In the same man- 
ner fill the other burette with the N/5 HCl solution. 
Titrate the one solution agamst the other, using methyl 
orange as an mdicator and the same volumes as in the 

[12] 



equivalent volume work (10 cc. of the solution diluted 
to 50 cc, etc.). Run duplicate determinations. Calculate 
and report grams of NaOH per cubic centimeter of the 
unknown solution. 

Experiment No. 8 

DETERMINATION OF THE STRENGTH OF AN UNKNOWN 
ACID SOLUTION 

Perform as in preceding experiment, using your stand- 
ard N/10 NaOH solution. Run duplicate determinations. 
Calculate and report grams of HCl per cubic centimeter 
of the unknown solution. 

Experiment No. 9 

DETERMINATION OF THE STRENGTH OF AN UNKNOWN 
K2CO3 SOLUTION, USING METHYL ORANGE AS INDICATOR 

Measure out, Avith burette, two 20 cc. portions of the 
unknown K.^CO^ solution, dilute with 50 cc. of distilled 
water, and titrate in the same manner as with Na.^CO^ in 
Experiment No. 6. Make at least two trials, and more if 
necessary to make titrations check. Calculate and report 
the amount of K^COg and also its equivalent m K^O per 
cubic centimeter of the unknown solution. 

K^COg + 2 HCl = 2 KCl + Hp + CO^ 

Experiment No. 10 

DETERMINATION OF THE STRENGTH OF AN UNKNOWN 
K2CO3 SOLUTION, USING PHENOLPHTHALEIN AS INDICATOR 

Measure out, with burette, two 20 cc. portions of the 
unknown K2CO3 solution, dilute with 50 cc. of distilled 
water, and titrate in the same manner as in Experiment 

[18] 



No. 9, using phenolphthalein as indicator. Calculate and 
report the amount of K^CO^ and its equivalent in K^O 
per cubic centimeter of the unknown solution. The 
phenolphthalein indicates only half the carbonates, as 
indicated by the equation 

K^CO^ + HCl = KHCO3 + KCl 

Experiment No. 11 

DETERMINATION OF THE STRENGTH OF AN UNKNOWN 
NaOH AND Na^COg SOLUTION 

In the preceding experiments it was shown that the 
hydroxides of sodium and potassium acted differently 
from the carbonates toward some indicators and that 
the carbonates acted differently with different indicators. 
When phenolphthalein is used as indicator, all the metal 
of the hydroxide is neutralized, while only half is neutral- 
ized in the carbonate. When methyl orange is used as 
mdicator, all the metal of hydroxide and carbonate is 
neutralized. It ouglit, therefore, to be possible to tell the 
amount of a carbonate in a solution of a hydroxide by 
making titrations, using methyl orange and phenolphthalein 
as indicators. 

jNIeasure out, with burette, 10 cc. of the unknown solu- 
tion; dilute with 50 cc. of distilled water; and titrate, using 
phenolphthalein as indicator,* noting the cubic centimeters 
of acid required. Measure out another portion of 10 cc, 
and titrate, usmg methyl orange as indicator. The phenol- 
phthalein shows all the hydroxide and half the carbon- 
ate ; the methyl orange shows all the hydroxide and all 
the carbonates. From data obtained calculate and report 

* Prepared according to directions on page 88. 

[1^] 



the amounts of carbonate and hydroxide per cubic centimeter 
of the unknown sohition. Write all equations illustrating 
the reaction and give methods of calculatmg results. 

Question 

Discuss the use of indicators. 

References 

CoHN. Indicators and Test Papers. 

Morse. Exercises in Qiiantitative Analysis, pp. 110-115. 
NoYES, W. A. A Textbook of Chemistry, pp. 387-390. 
Stieglitz. Journal of A/nerican Chemical Society, Vol. XXV, 

p. 1114. 
Sutton. Volumetric Analysis. 
TizARD. Indicators. 
Treadwell-Hall. Analytical Chemistry, Vol. II, \)^. 426-435. 

Experiment No. 12 

DETERMINATION OF ACETIC ACID IN VINEGAR 

The formula of acetic acid is HC^HgO^. It has one re- 
placeable hydrogen atom. Take 5 cc. of vinegar, measured 
by means of a burette or pipette, dilute to 100 cc. with 
distilled water, and titrate with your standard N/10 NaOH 
solution. Run duplicates. Use phenolphthalein as the 
indicator m the titration. Calculate and report grams of 
acetic acid in 1 cc. of the vinegar. 

Questions 

1. Considering that 1 cc. of vinegar weighs 1 g., what is the 
per cent of acetic acid in the sample of vinegar examined ? 
2. What is the standard in your state and in the United 
States for pure vinegar as to acidity and total solids ? 

Reference 

Leach. Food Inspection and Analysis (3d ed.), p. 772. 1914. 

[15] 



Experiment No. 13 

DETERMINATION OF TOTAL SOLIDS IN VINEGAR 

Weigh a small porcelain evaporating dish which has 
been previously cleaned and dried. Measure out exactly, 
with a burette, 10 cc. of the sample of vinegar to be 
analyzed, and evaporate this to dryness on a water bath ; 
then dry for three hours in a water oven (or drying oven) 
at the temperature of boiling water. Cool the dish and 
solids ui desiccator, and weigh. From the figures obtained 
.calculate and report the percentage of total solids in the 
sample. Make two determinations. 

Question 

What is indicated by a low total-solids content ? Discuss. 

Experiment No. 14 

DETERMINATION OF ASH IN VINEGAR 

Take the solid residues from the previous experiment 
and ignite over a low flame until you obtain a grayish- 
white ash. Cool the dish and ash in desiccator, and 
weigh. The weight obtained minus the weight of the 
dish represents the weight of the ash in the amount of 
vineorar used. From the results obtained calculate and 
report the percentage of ash in the sample. jNIake two 
determinations. Test for water-soluble phosphates. Also 
test for phosphates insoluble in water but soluble m 
dilute hydrochloric acid. 

An Argand burner with mica cliimney or an electric 
muffle furnace may be successfully used for ashing. The 

[16] 



flame is kept low until charring is complete, then turned 
as high as it can be raised without smoking. 

Questions 

1. Explain the relationship of phosphates to the purity of 
vinegar. 2. Give a quick method for the manufacture of 
vinegar, 3. Explain the conditions necessary for the making 
and keeping of apple vinegar. 4. Compare the composition of 
cider with that of cider vinegar. 

Reference 

Leach. Food Inspection and Analysis (3d ed.), pp. 759-782. 1914. 

Experiment No. 15 

PREPAEATION OF STANDARD POTASSIUM PERMANGANATE 
SOLUTION (KMnO^) 

Dissolve 3.25 g. of KMnO^ in 1 liter of distilled water. 
Let the solution stand until the next laboratory period, 
and then filter through a properly prepared perforated 
or Gooch crucible (prepared as in Exp. No. 5, Part I). 
Standardize the KMnO^ solution against a known solution 
of ferrous ammonium sulphate (FeSO^ • (NH^)2S0^ • 6 H^O) 
as follows: 

Place 3.5 g. (exactly weighed) of C. P. ferrous ammon- 
ium sulphate in a 200 or 250 cc. measuring flask, and make 
up to the mark with distilled water. Shake until the salt 
is completely dissolved. By means of a pipette or burette 
measure out 50 cc. of the ferrous ammonium sulphate solu- 
tion into a beaker, add 25 cc. of sulphuric acid (H^SO^) 
strength 1 : 4, and dilute to about 100 cc. with distilled 
water. Add the KMnO^ solution from a burette until 
one drop gives a permanent pink color. At least three 
titrations should be made. From the data obtained and 

[17] 



the following equation calculate the amount of iron (Fe) 
oxidized by 1 cc. of the KMnO^ solution. 

FeSOJ 
(NH^)^SO^ +KMnO,+H,SO =Fe/S0^)3+K^S0^+MnS0^ 
6 HP J +(NH^)^SO^+Hp 

(Balance the equation.) 

Observe that one seventh of the iveight of the ferrous 
ammonium sulphate is iron {Fe^, 

Questions 

1. Show that one seventh of the weight of ferrous anniio- 
nium sulphate is iron. 2. How many grams of KMnO^ would 
be required for a N/10 KMnO^ solution ? How many grams 
of K^Cr^O^ would be required for a IST/IO K^CraO^ solution ? 
3. Problem : weight of iron ore taken is .2 g. ; volume of 
N/10 K^Cr^O^ required for titration is 20 cc. What is the 
percentage of Fe in the sample ? 

Experiment No. 16 

DETEEMINATION OF THE AMOUNT OF CALCIUM OXIDE IN 
LIMESTONE 

The sample of lime, limestone, or material containing 
calcium ground to a fine pov^der is thoroughly mixed, and 
approximately 2 g. of the mixture (exactly weighed) is 
placed in a beaker with 25 cc. of concentrated hydro- 
chloric acid (HCl) and 25 cc. of distilled water, li neces- 
sary, the solution is heated to get the calcium compounds 
in solution. Possibly all the material does not go mto 
solution, as the material may contain some silica (SiO^). 
The calcium salts are with a little heating readily dis- 
solved in the dilute acid. After the material is in solution, 
the solution in the beaker is transferred by filtering mto 

[18] 



a 200 or 250 cc. measuring flask. Distilled water is used 
to wash out the beaker and to wash any material in the 
filter free of any soluble substance. The solution in the 
measurmg flask is then made up to the mark with dis- 
tilled water, shaken until thoroughly mixed, and two por- 
tions of 25 cc. each are measured out by means of a 
pipette or burette and placed in two beakers. To each 
of the portions 25 cc. of distilled water is added, then 
ammonium hydroxide (NH^OH) solution is added until 
alkaline. The solution is heated to boiling, and while 
boiling a solution of ammonium oxalate * ((NH^)2C20^) is 
added dropwise until the calcium is completely precipi- 
tated as calcium oxalate. The complete precipitation of 
the calcium is determined by allowing the precipitate to 
settle, and adding a drop of the ammonium oxalate solu- 
tion to the supernatant liquid. If the precipitation is not 
complete, a precipitate will be formed ; in which case the 
solution is to be treated again as at first. 

Allow the precipitate to settle, filter wdiile hot, and 
wash free from soluble oxalates, usmg hot water. The 
precipitate in the beaker should be thoroughly washed 
free of soluble oxalates, but it does not need to be com- 
pletely transferred to the filter paper, as the filter paper 
and precipitates are later to be returned to the same 
beaker in which the precipitation took place. After the 
precipitate in the beaker and in the filter paper is thor- 
oughly washed, return the filter paper and precipitate to 
the beaker from which it was filtered, add about 50 cc. of 
water and 10 cc. of sulphuric acid (1 : 1), heat nearly to 
boiling, and titrate with the standard KMnO^ solution 
until you get a permanent pink color. 

* Prepared according to directions on page 89. 

[19] 



Precaution. Do not heat the solution to boiling, but 
bring it nearly to boiling. Explain. Save standard 
KMnO^ solution for other experiments. 

Calculation of Results 

Write all equations for the solution of the calcium com- 
pound and its precipitation. The reaction with KMnO^ 
gives the following equation: 

CaCp^ + H^SO^ + KMnO, 

= CaSO^ + MnSO, + K^SO^ + CO^ + H^ 
(Balance the equation.) 

By comparing the equations for oxidation of Fe and 
CaCgO^, it will be seen that the same amount of KMnO^ 
oxidizes twice as much of the iron compound as of 
the calcium oxalate. As the molecular weight of CaO 
and the atomic weight of Fe are about the same, the 
factor for hon divided by 2 gives the factor for CaO ; 
or the titre of KJNInO^ in terms of Fe divided by 2 
gives the titre of KMnO^ in terms of CaO. Calculate 
and report from the results the percentage of CaO in 
the sample. 

Questions 

1. If you had a sample of pm-e limestone, what per cent of 
CaO should you obtain by its analysis ? 2. How many pounds 
of CaO and Ca(0H)2 are equivalent to 100 lb. of air slaked 
lime ? 3. One cubic centimeter of N/IO KMnO^ solution will 
oxidize .0056 g. of iron (Fe). If .2 g. of a sample of barium 
oxalate requires 10 cc. of the KMnO^ solution, what is the 
percentage of barium oxalate in the sample ? 



[20] 



PART II 

ANALYSIS OF FEEDSTUFFS 

Preparation of a Sample of Feedstuff for 
Analysis 

The sample of feedstuff should be prepared for analysis 
by grinding the material to pass through a sieve having 
circular perforations 1 mm. in diameter. After sample is 
prepared and thoroughly mixed, it should be kept in a 
well-stoppered bottle. Enough of the sample should be 
prepared for the complete analysis. 

Experiment No. 17 

determination of moisture in feedstuffs 

Weigh out exactly 2 g. of the feed sample in a weighed 
watch glass, and dry for three hours in a water oven at 
the temperature of boiling water ; cool in desiccator, and 
weigh rapidly. Heat again, and weigh at intervals of 
one-half hour until the material ceases to lose weight. 
Make duplicate determinations. Calculate and report the 
percentage of moisture in the sample. 

Question 

Why heat at the temperature of boiling water, as specified, 
instead of at the temperature of 100° C. ? 

[21] 



Experiment No. 18 

DETERMINATION OF ASH IN FEEDSTUFFS 

The residue from Experiment No. 17, or a weiglied 
amount (from 2 to 3 g.) of tlie original material, is ignited 
gently over a small flame in a weighed porcelain crucible to 





A 


1 


■■pps-r^ ■' 








ELECTRIC DRYING OVEN 
An accurate, inexpensive, and convenient type 

a constant weight. Be sure to weigh the crucible before 
placing the weighed sample of feed in it. Make dupli- 
cate determinations. Calculate and report the percentage 

[21!] 



of ash in the sample examined. Make a quahtative analy- 
sis of plant ash for essential elements of plant food, and 
report results. 

Question 

What value has the ash determination in the analysis of 
feedstuff ? 

Experiment No. 19 

DETERMINATION OF CRUDE PROTEIN IN FEEDSTUFFS 

Apparatus 

Kjeldahl flasks of 800 cc. for both digestion and distilla- 
tion, a safety bulb, and a condenser. 

Weigh out accurately a convenient quantity of the feed 
sample (from 0.7 to 1.4 g.) and transfer it to the Kjeldahl 
flask. The neck of the flask should be dry, so that none 
of the material sticks on the neck. Add 25 cc. of concen- 
trated C. P. H^SO^ and approximately 0.3 g. of CuSO^. 
Support the flask in a sloping position on a wire gauze 
or on a piece of asbestos board with a hole in the 
center. Heat gradually to boiling with a Bunsen flame 
(heatmg should be done in a hood or some arrangement 
made to remove the fumes so they will not get into the 
room).* As soon as the acid is boiling freely and any 
frothing has ceased, remove the flame ; and when the con- 
tents have cooled, add about 5 g. of C. P. K^SO^. The 
heating is renewed and continued until the material is 
completely oxidized. This will be shown by the acid's 
becoming clear and having only a slight blue or green 
tint. After removing the flame a few small pieces of 

* Fumes can be removed by means of an earthenware or lead fume 
duct or by means of a Sy fumeless digestion apparatus. 

[23] 



KMnO^ may be added to make sure that the oxidation 
is complete. This should be added until it permanently 
colors the solution. The flask and contents are allowed 
to cool completely, then 200 to 250 cc. of distilled water 
is added. Through a thistle tube which should reach to 
the bottom of the flask, or by slanting the flask and pour- 
ing doAvn the side, there is now added about 75 cc. of 




KJELDAHL DIGESTION APPARATUS 



concentrated NaOH solution * (free of carbonates). Do 
not shake the solution in the flask before it is connected 
with the safety bulb and distillation apparatus. A small 
piece of granulated zinc or a little zinc dust is added 
to prevent bumping in the subsequent distillation. Insert 
the safety bulb in the flask and connect with a condenser. 
Gently shake the flask to mix its contents, and distill the 
ammonia mto a measured amount (25 cc.) of the standard 
* Prepared according to directions on page 89. 

[24] 



N/5 HCl solution (acid must be measured exactly from 
a burette). The receiver may conveniently be a 250 cc. 
Erlenmeyer flask. The end of the distillation tube should 
extend down into the standard HCl solution. When about 
100 cc. have been distilled over, making a volume of approx- 
imately 125 cc. in the flask, the distillation may be stopped. 




KJELDAHL DISTILLATION APPARATUS (STEAM) 



Caution. Before removing the flame from under the 
distilling flask or cutting off the steam (if steam is used 
for the distillation) remove the receiving flask so as to 
keep the liquid from being sucked back into the distilling 
flask when the flame is removed. Titrate the distillate 
with your standard N/10 NaOH solution, and from the 
data obtained, calculate the percentage of nitrogen in the 
feedstuff. The indicator, which should be cochineal or 
methyl red^ may be placed in the receiver with the acid 

[25] 



at the beginning of the distillation. Should tlie indicator 
show an alkaline reaction during the distillation, it means 
that not enough acid has been used to neutralize all the 
ammonia distilled. Multiply the percentage of nitrogen 
by 6.25 to obtain the percentage of crude protein in the 
sample. Run duplicate determinations. The duplicate 
nitrogen determmations should check within .02 per cent. 

Note. Accurate work requires that a blank digestion and 
distillation be made with some substance that is nitrogen free, 
in order to test the purity of the reagents. 

Questions 

1. Give reasons for the use of each substance in the de- 
termination of nitrogen. 2. Why multiply the percentage 
of nitrogen by 6.25 to obtain the percentage of crude protein ? 
Discuss. 

Experiment No. 20 

DETERMINATION OF ETHER EXTRACT (FAT) IN 
FEEDSTUFFS 

Apparatus 

One extraction thimble and extraction apparatus. 

Place 2 or 3 g. (weighed exactly) of the sample of 
feedstuff in an extraction thimble, and a small piece of 
cotton in the opening of the thimble to hold the feedstuff 
in and also to distribute the ether during the extraction. 
Dry the thimble containing the feedstuff in the oven at 
the temperature of boiling water for two hours, to remove 
the moisture, and then extract with anhydrous, alcohol- 
free ether* for twelve hours. Use apparatus for the ex- 
traction as illustrated in the lectures or specified by 
the instructor. The receiving flask for the fat should be 
cleaned, dried, and weighed before the extraction is begun. 
* Prepared accordiuo; to directions on page 89. 

[20] 



After the extraction is complete, evaporate off the ether on 
a water bath from the receiving flask (recovering the ether, 
if possible), and dry the extract in the weighed vessel at 




EXTKACTlUN APi'AKAJ L8 iuK DETiiiUli^ATluN OF FAT 
(ETHER EXTRACT) 

the temperature of boiling water for one-half hour; cool 
in desiccator and weigh. Repeat the drying and weighing 
at half-hour intervals until a constant minimum weight 
is obtained. The increased weight of the flask over the 
original weight of the flask when clean, empty, and dry 
is due to the weight of the fat extracted. 

[27] 



Example 

Let X = amount of feedstuff used. 

Let y — weight of flask plus weight of fat. 

Let z = weight of flask when empty, dry, and clean. 

Then y — z — weight of fat in x g. of feedstuff. 

— — ~ X 100 = percentage of ether extract (fat) in the feedstuff. 



X 



Make duplicate determinations. Calculate and report the 
percentage of ether extract in tlie sample of feedstuff. 

Note. The term ether extract is used to represent the materials 
that are soluble in ether. Besides fats and oils the ether extract 
generally contains some waxes, resins, chlorophyll, coloring matters, 
and, in some cases, phosphorized fats and fatlike bodies containing 
both nitrogen and phosphorus. 

Questions 

1. What is ether ? 2. How is it made ? 3. What are some 
of its properties ? 4. What impurities would most likely be 
found in ether ? 5. How can these impurities be most conven- 
iently eliminated ? 6. What are sulphuric ether and petroleum 
ether ? 7. Name the other solvents which may be used for the 
extraction of fat, besides ether, and give the temperature at 
which each boils. 8. Why is the heating value of a fat higher 
than that of a carbohydrate? 9. Why is the feedstuff dried 
before the extraction of fat, and why is anhydrous, alcohol- 
free ether used? 

Experiment No. 21 

PREPARATION OF A L25 PER CENT H.SO^ SOLUTION AND 
A 1.25 PER CENT NaOH SOLUTION 

A 1.25 per cent sulphuric acid solution contains 12.5 g. 
H^SO^ per liter. Determine the specific gravity of the 
C. P. concentrated sulphuric acid, and calculate the num- 
ber of cubic centimeters of this solution that will contain 
12.5 g. of H^SO^ (see Appendix, p. 85). Measure out the 

[28] 



calculated amount in a graduated cylinder, and dilute 
to one liter with distilled water. Titrate this solution 
against your standard alkali, and adjust the strength, if 
necessary, until the solution contains 0.0125 g. of H^SO^ 
per cubic centimeter. 

Weigh out the amount of NaOH (sticks, free of car- 
bonates) requued for a liter of a 1.25 per cent NaOH 
solution (the sticks of NaOH generally contain from 10 
to 20 per cent water). Shake thoroughly until the NaOH 
is dissolved. Titrate this solution against the 1.25 per cent 
H,SO^ solution, and adjust the strength until correct. 

Questions 

1. 10 cc. of 1.25 per cent H,SO^ = (?) cc. N/10 NaOH ? 

2. 10 cc. of 1.25 per cent NaOH = (?) cc. N/5 HCl ? 

3. 10 cc. of 1.25 per cent H^SO, = (?) cc. 1.25 per cent NaOH ? 

Experiment No. 22 

DETERMINATION OF CRUDE FIBER IN FEEDSTUFFS 

Apparatus 

One 500 cc. Erlenmeyer flask ; one condenser ; two 
Gooch crucibles; 1.25 per cent H^SO^ solution; 1.25 per 
cent NaOH solution. 

Place the residue from Experiment No. 20 in a 500 cc. 
Erlenmeyer flask. Add 200 cc. of boiling 1.25 per cent 
H^SO^ solution, connect with a reflux condenser, and boil 
gently for thirty minutes. Filter through a Gooch cruci- 
ble containing a small quantity of asbestos, or a Biichner 
funnel, using closely woven linen as a filter. Wash with 
boiling water until the washings are free from acid. Rinse 
the substance remaining in the crucible or on the linen 
back into the Erlenmeyer flask with 200 cc. of a boiling 

[29] 



solution of 1.25 per cent NaOH (free from carbonates). 
Boil at once for thirty minutes as before. As soon as the 
boiling is completed, filter through a Gooch crucible or 
Blichner funnel, as before, wash several times with boiling 
water, once with dilute HCl (1 : 1), and then with boiling 
water until the washings are free from acid and are neutral. 
If hnen is used as the filter, tlie material remaining on the 
linen has to be transferred to a porcelain crucible before 
drying. Dry the porcelain crucible or Gooch crucible 
containing the crude fiber, asbestos, and mineral matter 
in an oven at the temperature of 110° C. until completely 
dry, and weigh to constant weight. Then ignite the 
material in the porcelain crucible or Gooch crucible with 
a Bunsen flame, cool the crucible in a desiccator, and weigh 
to constant weight. The loss in weight represents the 
weight of the crude fiber in the sample of feedstuff exam- 
ined. Make duplicate determinations. Calculate and report 
the percentage of crude fiber in the sample of feedstuff. 

Questions 

1. What is crude fiber ? 2. Is it a compound or a mixture ? 
3. What substances are removed by each digestion ? 4. Why 
boil for a specified time ? 5. Why are the solutions of acid 
and alkali of tliis particular strength used, and why are they 
used in a certain order ? 6. Discuss the value of the crude- 
fiber determination in the consideration of the analysis of a 
feedstuff. 

Experiment No. 23 

DETERMINATION OF NITROGEN-FREE EXTRACT IN 
FEEDSTUFF 

Nitrogen-free extract is usually obtained by difference. 
Subtract from 100 per cent the sum of the percentage of 
moisture, ash, ether extract (fat), crude fiber, and crude 

[80] 



protein. The result is the percentage of nitrogen-free 
extract in the sample. 

Report the results in the following form: 

Determination No. 1 Determination No. 2 

Moisture 

Ash 

Ether extract 

Crude fiber 

Crude protein 

Total X Total x' 

100 — X = percentage of nitrogen-free extract. 

Questions 

1. What substances constitute the nitrogen-free extract? 
2. Make a comparison of the analyses of two samples of feed- 
stuff of the same kind, and give reasons for conclusions in 
regard to their feeding value. 3. A sample of feedstuff weigh- 
ing 200 g. after being air-dried weighed 50 g. The analysis of 
the air-dried sample was as follows : 

Moisture 4.40% 

Crude protein 10.75% 

Ether extract (fat) 1.15% 

Nitrogen-free extract 64.86% 

Crude fiber , 12.82% 

Ash 6.02% 

Report the analysis on the basis of the original material 
and also on the moisture-free basis. 



[31] 



PART III 

CHEMICAL ANALYSIS OF SOIL 

Directions for taking a Sample of Soil for 
Analysis * 

Remove the surface accumulations of decaying leaves, 
etc., and take samples with a soil tube or auger to the 
desired depth. All samples of soils taken for analysis 
should be composite, and should be composed of represent- 
ative samples taken from at least five different places in 
the field sample, each individual sample to be a column 
of uniform soil extending through the stratum sampled. 

One composite sample should be taken from each im- 
portant and distinctly different soil stratum to a depth 
of 40 in., or 1 m., including a composite sample from the 
arable stratum, or plowed soil, usually about 6 in., or 
15 cm., deep. 

If the plow line and subsoil coincide, and the subsoil 
is fairly uniform stratum to a depth of about 40 in., then 
only two composite samples need be taken — one of the 
arable soil and one of the subsoil. But if the subsoil 
line is lower than the plow line and not below 40 in., then 
both strata below the arable soil should be sampled, which 

* Bulletin No. 107 (Revised), Bureau of Chemistry, United States 
Department of Agriculture. 

[32] 



would make three composite samples from the field: one 
from the surface or arable soil, one from the subsurface 
soil (that is, from the stratum between the plow Ime 
and the true subsoil), and one from the true subsoil. 
Dry the samples in a well-aired, cool place. 



APPARATUS USED IN THE ANALYSIS OF SOILS 

i, weighing bottle; ^, measuring flasks (250 cc, 500 cc, and 1000 cc); 

5, water bath and tripod ; 4, mortar and pestle ; 5, suction flask, funnel, 

and Gooch crucible; 6, humus cylinder (500 cc.) ; 7, flask with reflux 

condenser ; S, sieve (holes 1 mm. in diameter) 

Preparation of Samples for Analysis 

Prepare the laboratory sample by putting it through a 
sieve with round holes of 1 mm. diameter, using a rubber- 
tipped pestle to pulverize the lumps. Weigh, and discard 
the remaining material. Keep the sample in a cool place, 
and stopper to prevent change in condition. The fine soil 

[83] 



that passes through the holes of the sieve is used for the 
chemical analysis. Record the weight of the fine and the 
coarse soil as obtained. 

Question 

Why is the weight of the fine and the coarse soil desired ? 

Experiment No. 24 

QUALITATIVE ANALYSIS OF SOIL 

Place about 10 g. of soil in a beaker ; then add 25 cc. 
of distilled water and 25 cc. of C. P. concentrated HCL 
Cover the beaker with a watch glass and heat on a sand 
bath, wire gauze, or hot plate in the hood for two hours, 
replacing the acid if excessive evaporation takes place. 
Dilute with 50 cc. of distilled water, heat to boiling, and 
filter the solution, washing the residue with hot water. 
The insoluble residue consists mainly of silica and insol- 
uble silicates. Evaporate the filtrate to dryness to remove 
silica from the solution, take up with 25 cc. hot water con- 
taining 5 cc. of HCl, and filter, washing the residue with hot 
water. Divide the filtrate into two portions : To Portion A 
add ammonium hydroxide (NH^OH) until alkaline. The 
precipitate may contain Fe(OH)g (red), A1(0H)3 (white 
and flocculent), and calcium phosphate (Ca^ (PO J^) (white). 
Filter and test precipitate for iron and aluminium. Make 
the filtrate alkaline with NH OH and add the ammonium 

4 

oxalate (^(l^}i^}^Cfi^^ solution. A white precipitate of 
calcium oxalate (CaC^O^) may form, showing the presence 
of calcium. Make the filtrate from the calcium oxalate 
precipitation slightly acid with dilute HCl (1 : 1), con- 
centrate to a volume of about 30 cc, add 5 cc. of sodium 

[34] 



ammonium hydrogen phosphate,* and then add gradually 
NH^OH until the solution is distinctly alkaline. If the 
soil contains a very small quantity of magnesium, it may 
be necessary to let the solution stand for a short time 
to obtain a precipitate. Evaporate Portion B nearly to 
dryness ; add 20 cc. of water, make alkaline with NH^OH, 
and then slightly acid with dilute HNO^ (1:1). Warm 
to approximately 70° C. and add a few cubic centimeters of 
ammonium molybdate ((NH^)2^1oO^). A yellow precipitate 
of ammonium phosphomolybdate ((NH^)gPO^ • 12 MoO^) 
proves the presence of phosphates. Also test the original 
soil for carbonates. JNIake a detailed report of results, 
writing all equations illustrating the reactions. 

Questions 

1. In what chemical forms do the elements exist in a soil ? 
2. From what is the inorganic material or mineral matter of 
soils derived ? 3. What elements are liable to be deficient in 
soils ? 

Experiment No. 25 

DETERMINATION OF MOISTURE IN SOIL 

Dry 2 to 5 g. of air-dried soil in a weighed watch glass 
for five hours at the temperature of boiling water, cool in 
a desiccator, and weigh rapidly to avoid absorption of 
moisture from the air. Heat agam, and weigh at intervals 
of one hour until the material ceases to lose weight. 
Calculate and report the percentage of moisture in the soil. 

* Prepared according to directions on page 89. 



[35] 



Experiment No. 26 

DETERMINATION OF VOLATILE MATTER IN SOIL 

Weigh out 2 to 5 g. of air-dried soil in a weighed por- 
celain crucible and heat to redness until all organic matter 
is burned. Cool the crucible containing the soil in a des- 
iccator, and weigh. Contmue the burning, cooling, and 
weighing until constant weight is obtained. If the soil 
contains appreciable quantities of carbonates, it should 
be moistened after cooliQg with a few drops of ammonium 
carbonate, dried, heated to dull redness to expel ammo- 
nium salts, cooled in desiccator, and again weighed. The 
loss in weight represents the hygroscopic moisture (see 
Exp. No. 25), water of combination, organic matter, am- 
monium salts, etc. From this loss, calculated as percentage, 
subtract the percentage of moisture as determined m Exper- 
iment No. 25 and obtain the percentage of matter volatile 
above 100° C. Make duplicate determinations. Calculate 
and report the percentage of volatile matter in the soil. 

Question 

Give the reason for the use of ammonium carbonate. 

Experiment No. 27 

DETERMINATION OF HUMUS IN SOIL 

Place 10 g. of the soil sample in a Gooch crucible or 
on a filter paper in a funnel, and wash with dilute HCl 
(1 cc. concentrated acid to 40 cc. H^O) until the filtrate 
after being made alkaline with NH^^OH gives no pre- 
cipitate with ammonium oxalate (^(l:^ll^^JJfi^^ solution. 

[36] 



Wash with distilled water until free from acid. Transfer 
the contents of the crucible or funnel into a glass-stoppered 
cylinder, with 500 cc. of a 4 per cent NH^OH solution 
(1 cc. concentrated ammonia (sp. gr. .9) to 13 cc. of water), 
and allow it to remain, with occasional shaking, for twenty- 
four hours. During this time the cylinder should be 
inclined as much as possible without bringing its contents 
in contact with the stopper. Shake thoroughly and place 
the cylinder in a vertical position, add 2.5 g. of (NH^)2C0g, 
and leave it for at least twelve hours to allow the sedi- 
ment to settle. Filter the supernatant liquid (that is, re- 
move the liquid above the sediment without stirring the 
sediment up ; the filtrate will be colored, but should be 
free from any sediment), evaporate an aliquot portion (say 
50 cc.) to dryness in a small porcelain evaporating dish on 
a water bath, dry at 100° C, and weigh. Ignite the residue, 
cool the dish in a desiccator, and weigh again. Calculate 
and report the percentage of humus in sample. 

Questions 

1. What is humus ? 2. What are humates ? 3. What is humic 
acid? 4. Give reasons for each step in the determination. 
5. Of what value is the humus determination ? 6. Discuss 
the relation of organic matter in soils to fertility. 

Experiment No. 28 

DETERMINATION OF NITROGEN IN SOIL 
(NITRATES ABSENT) 

Place 7 g. of soil in an 800 cc. Kjeldahl digestion flask 
with 30 cc. concentrated C. P. sulphuric acid, and continue 
as in Experiment No. 19. Make duplicate determina- 
tions. Calculate and report the percentage of nitrogen. 

[37] 



Experiment No. 29 

TEST rOR ACIDITY OR ALKALINITY OF SOIL AND 
DETERMINATION OF LIME REQUIREMENTS 

Place about 10 o". of soil in a beaker and add 75 cc. dis- 
tilled water. After evaporating the filtrate to an approxi- 
mate volume of 20 cc., stir for about five minutes and filter. 
Test the filtrate with phenolphthalein indicator to see if the 
solution is alkaline or acid. If the solution is alkaline, then 
determine whether it is due to Na„COg, Na.^SO^, or CaCO^ 
in solution. If the solution is acid, then proceed as follows : 
Slake a small piece of lime (CaO) until it falls to a fine 
powder. This is best done by adding a few drops of water 
at a time, continuing until enough has been added to slake 
the lime thoroughly. With the slaked lime (Ca(OH)„) 
make a saturated solution of lime water by the addition of 
approximately 250 cc. of warm water. Let the solution cool 
by standing; filter, and transfer the filtrate immediately to a 
glass-stoppered bottle. Titrate a portion of the clear solu- 
tion with your standard HCl solution. Calculate and report 
the grams of CaO per cubic centimeter of limewater. 

The standardized limewater may be used to determine 
the lime requirements or the acidity of the soil as follows : 
Weigh out two portions of 10 g. each, weighing only to 
the second decimal place ; place them in two porcelain 
dishes of about 100 cc. capacity and moisten with about 
75 cc. of distilled water ; then to one add 5 cc. and to the 
other 10 cc. of the clear limewater solution from burette 
or pipette. Stir well, allow to stand about one hour, and 
then dry on a water bath. Add 50 to 75 cc. of distilled 

[88] 



water, stir thoroughly, and filter. About 30 cc. of the 
filtrate is then placed in a porcelain dish, three drops of 
neutral phenolphthalein added, and the solution boiled 
over a direct flame until about 10 cc. remains in the dish. 
The portion showing the alkaline color of phenolphthalein 
with the least amount of lime water has been saturated with 
lime. The portion showing no color is still acid or neutral. 

Next weigh out four more portions of soil and treat 
with limewater in a similar way, using for the first 1 cc. 
more of limewater than was used in the portion that did 
not show alkaline, for the second 2 cc. more, etc. These 
are carried through as in the first series. 

Note the least number of cubic centimeters of limewater 
that saturated the 10 g. of fine soil. From the data ob- 
tained, calculate and report the lime (CaO) required per 
acre of soil, using 2,000,000 lb. as the weight of an acre 
of soil 8 in. in depth. Also calculate the amount of ground 
limestone required per acre of soil. 

Questions 

1. Discuss soil acidity and alkalinity, including causes and 
correction. 2. If a soil solution tests acid with phenolphthal- 
ein as indicator when cold, and alkaline after boiling, what 
does this indicate ? 3. Discuss the relation of the acidity of 
soils to soil fertility. 4. Give a complete discussion of alkali 
soils and the methods of correcting them. 

Experiment No. 30 

STRONG HYDROCHLORIC ACID (SP. GR. 1.115) DIGESTION OF 
SOIL. PREPARATION OF SOIL SOLUTION 

Weigh out exactly 10 g. of soil, transfer to an Erlen- 
meyer flask of non soluble glass of 200 to 300 cc. capacity, 
and add 100 cc. of hydrochloric acid of constant boiling 

[39] 



point (sp. gr. 1.115) made, approximately, by diluting 
58 CO. of ordinary concentrated HCl (sp. gr. 1.20) with 
42 cc. of distilled water. The flask should be provided 
with a rubber stopper containing a glass tube about 
20 in. in length. Place the flask containing the soil and 
acid in a water bath and digest for ten hours, shaking 
every hour while digesting. After the digestion is com- 
plete, allow the insoluble residue to settle, and decant the 
solution into an evaporating dish. Very small quantities 
of sediment passing over Avill do no harm. Wash the 
insoluble residue onto a filter with liot water, and con- 
tinue the washing until free from clilorides, adding the 
washings to the original solution for evaporation. (It is 
advisable to let each portion in the filter paper run 
through each time before adding any more water.) After 
the addition of a few drops of nitric acid, to oxidize the 
organic matter in solution, evaporate the solution to dry- 
ness on a water bath. Take up with hot water and a few 
cubic centimeters of hydrochloric acid and again evaporate 
to complete dryness. When the evaporation is completed 
and the dish cooled, add a few drops of strong hydrochloric 
acid, sufficient only to saturate the residue. Add about 
20 cc. of water, warm on a water bath to secure complete 
solution, and filter, washing until free of chlorides. Again 
evaporate the solution to dryness, to render insoluble any 
silica that may be in solution, take up with hydrochloric 
acid and water as before, and filter into a 500 cc. meas- 
uring flask, washing the residue free from chlorides. Make 
the solution in the measuring flask up to the mark with dis- 
tilled water, shake thoroughly, and designate as Solution A. 



[40] 



Experiment No. 31 

DETERMINATION OF IRON (Fe) IN SOIL SOLUTION BY 
VOLUMETRIC METHOD 

Measure out, with a burette or pipette, two 50 cc. 
portions of Solution A, place in beakers, heat nearly to 
boiling, and add NH^OH, drop by drop, until the solu- 
tion is strongly alkaline. Boil for two minutes, and filter 
while hot through a properly prepared Gooch crucible, 
washing several times with hot water (save filtrate and 
washings for Exp. No. 32). Transfer the precipitate and 
asbestos to the same beaker from which it was filtered, 
and add 25 cc. of H^SO^ (1 : 4) to dissolve the precipitate. 
To this solution add a small amount of granulated zinc 
or zinc dust and boil until all traces of zinc have dis- 
appeared and the iron is completely reduced. Titrate the 
solution immediately with your standard KMnO^ solution. 
If the reduced iron solution is allowed to stand exposed 
to the air before titrating, it will become oxidized. From 
the results obtained, calculate and report the percentage 
of iron in the soil sample soluble in the acid solution. 

Questions 

1. Give the reason why KMnO^ acts as its own indicator. 
2. What effect would a small amount of zinc in the solution 
have on the determination ? 3. Write equations illustrating 
all the reactions, and explain each step. 



[41] 



Experiment No. 32 

DETERMINATION OF CALCIUM (Ca) IN SOIL SOLUTION BY 
VOLUMETRIC METHOD 

Evaporate the filtrate and wasliings from Experiment 
No. 31 to a volume of about 50 cc, make slightly alkaline 
with NH^OH, and while boiling add ammonium oxalate 
((NH^)2C20J solution dropwise until all the calcium is 
precipitated, then add 2 cc. in excess. Boil for five 
minutes, allow the precipitate to settle, and filter while 
hot on a filter paper, without using suction. Wash the 
precipitate and beaker free from soluble oxalates with liot 
ivater. Transfer filter paper and contents to the same 
beaker from which the precipitate was filtered, add 50 cc. 
of distilled water and 20 cc. of H^SO^ (1:1), heat nearly 
to boiling, and while still hot titrate with the standard 
KMnO^ solution. Calculate and report the percentage of 
lime (CaO) m the soil sample soluble in the acid solu- 
tion, and also its equivalent in calcium carbonate (CaCOg). 

Note. If preferred, the calcium can be determined directly 
upon Solution A in the following manner : Take 50 cc. of Solution 
A, make slightly alkaline with NH^OH, and just clear with dilute 
HCl, avoiding an excess. Heat to boiling, add powdered ammonium 
oxalate or ammonium oxalate solution until the calcium is all pre- 
cipitated, and let stand until cool (usually until the next period 
or overnight). Filter, wash, and titrate the precipitate as in the 
previous method. 

Question 

Write equations for all reactions taking place in the 
determination. 

[42] 



Experiment No. 33 

DETERMINATION OF PHOSPHORIC ACID (P2O5) IN SOIL 
SOLUTION BY GRAVIMETRIC METHOD* 

Measure out, with a pipette or burette, two 100 cc. por- 
tions of Solution A into beakers, and concentrate to a vol- 
ume of about one fourth. Make alkaline with NH OH, 
then add 10 cc. in excess, and make diglitly acid with 
HNO3 (1 : 1), using a small piece of litmus paper in the 
solution as indicator. Avoid much excess of nitric acid. 
Gradually add to 20 cc. of the ammonium molybdate solu- 
tion t the solution containing the phosphates, and place 
the beaker in the water bath at the temperature of 40° to 
60° C. (be sure to transfer the last trace of the phosphate 
solution from the beaker by rinsing with distilled water). 
When the precipitate has sufficiently settled, add a few 
cubic centimeters of the ammonium molybdate solution 
to the supernatant liquid, in order to be sure that all the 
phosphoric acid is precipitated. If any precipitate is pro- 
duced, add more ammonium molybdate solution and repeat 
the operation until all the phosphoric acid is precipitated. 
After standing for three hours at a temperature not above 
60° C, filter on a small filter paper and wash with cold 
water until free from acid. Dissolve the ammonium phos- 
phomolybdate precipitate on the filter paper by pouring a 
solution containing equal parts of ammonium hydroxide 
and hot water through the filter, receiving the solution 
in the beaker in which the first precipitation took place. 

* If desired, phosphoric acid (PoOg) can be determined by optional 
method (Exp. No. 33 a). 

t Prepared according to directions on page 89. 

[43] 



\ 



Be sure that all the yellow precipitate on the filter paper 
is dissolved, and do not allow the total volume of the 
filtrate to amount to more than 100 cc. Make the solu- 
tion slightly acid with hydrochloric acid, using a small 
piece of litmus paper in the solution as indicator, and then 
sKghtlT/ alkaline with NHpH. Cool the solution and add 
magnesia mixture * (from 10 to 15 cc.) from a burette or 
pipette, letting it run in at the rate of a drop per second, 
stirring the solution vigorously with a policeman, or rubber- 
tipped glass rod, at the same time. After fifteen minutes 
add 12 cc. of ammonium hydroxide (sp. gr. 0.90) and allow 
the solution to stand several hours — two hours is usually 
enough. (If more convenient, the solution may be covered 
with a watch glass and left until the next laboratory period 
before filtering.) Filter and wash the precipitate with 2.5 
per cent ammonia (NH3) solution until free from chlorides. 
After the precipitate is dried, place the filter paper and 
precipitate in a weighed crucible and ignite to whiteness. 
Cool in desiccator, weigh, and heat to constant weight. 
From the weight of magnesium pyrophosphate (Mg^P^Op 
calculate the weight and the percentage of phosphoric acid 
(P O5) in the soil soluble in the acid solution. 

Questions 

1. Write equations for each step in the determination. 
2. Discuss the term pJiosphoric acid (Vfi^ as used. 3. Show 
the difference between a 2.5 per cent ammonia solution and 
a 2.5 per cent ammonium hydroxide solution. 

* Prepared according to directions on page 91. 



[44] 



Experiment No. 33 a (Optional Method) 

DETERMINATION OF PHOSPHORIC ACID (P2O5) IN SOIL 
SOLUTION BY VOLUMETRIC METHOD 

Measure out, with a pipette or burette, two 100 cc. por- 
tions of Solution A into beakers, and concentrate to a 
volume of about one fourth. Make alkaline with NH^OH, 
then add 10 cc. in excess, and make slightly acid with 
HNO (1 : 1), using a small piece of litmus paper in the 
solution as indicator. Avoid much excess of HNOg. Grad- 
ually add to 20 cc. of the ammonium molybdate solution 
the solution containing the phosphates, and place the 
beaker in a water bath at the temperature of 40° to 60° C. 
(be sure to transfer the last trace of the phosphate solu- 
tion from the beaker by rinsing with distilled water). 
When the precipitate has sufficiently settled, add a few 
cubic centimeters of the ammonium molybdate solution to 
the supernatant liquid, in order to be sure that all the 
phosphoric acid is precipitated. If any precipitate is pro- 
duced, add more ammonium molybdate solution, and 
repeat the operation until all the phosphoric acid is pre- 
cipitated. After the solution containing the precipitate 
stands for three hours at a temperature not above 60° C, 
filter on a small filter paper and wash with cold water 
until free from acid. Transfer the precipitate and filter 
paper containing the precipitate back into the same beaker 
in which it was precipitated. From the burette add the 
standard NaOH solution until the yellow precipitate is 
completely dissolved. Add about 25 cc. of distilled water 
and a few drops of phenolphthalein indicator. 

[45] 



1. Should the solution be colorless with the indicator 
added, continue the addition of the NaOH solution until 
a permanent pink color is obtained ; that is, the end-point 
is reached. 

2. Should the solution be colored after the indicator is 
added, that is, alkaline, titrate with your standard HCl 
solution until the color is discharged, and then titrate 
with your standard NaOH solution until the end-point 
is obtained. 

In either case the total amount of NaOH used to dis- 
solve and titrate the yellow precipitate and also the total 
amount of standard HCl used should be recorded. The 
precipitate is dissolved in the standard NaOH solution 
according to the following equation: 

(NH^)3P0^ . 12 M0O3 + 23 NaOH 

= 11 Na^MoO^ -\- (NH J^MoO^ + NaNH^HPO^ -f 11 H^ 

Two parts of ammonium phosphomolybdate 

((NH^)3PO,.12Mo03) 

contain 1 part of phosphoric acid (PPj). 

MoL wt. PgOg : mol. wt. 46 NaOH : : a: : cc. of NaOH x the 
titre of the NaOH solution 

X = grams of phosphoric acid (PPg) in the ahquot portion 
of the soil solution. From the data obtained, the titre 
of the NaOH solution, and the equation, calculate and 
report the percentage of phosphoric acid (^f>^ iii the 
soil soluble in the acid solution. 

Question 

Give the reason for each step in the determination and 
write equations illustrating the reactions. 

[46] 






Experiment No. 34 

DETERMINATION OF POTASH (KgO) IN SOIL SOLUTION 
BY THE USE OF PLATINUM SOLUTION* 

Measure out, with a burette or pipette, two 100 cc. 
portions of Solution A, place in beakers, heat nearly to 
boiling, and add NH^OH, dy^o]? hy drop, until the solu- 
tion is strongly alkaline. Cover the beaker and boil the 
solution for about one minute ; if no ammonia is given off 
(detect by smelling), more is added, droij hy drop^ until it 
can be detected. Do not allow the precipitate to settle, 
but stir and filter immediately while hot, washing it 
thoroughly with liot water. Evaporate the filtrate and 
washings to complete dryness, heat below redness to expel 
ammonium salts, dissolve in about 25 cc. of hot water, 
add about 5 cc. of saturated barium hydroxide, and heat to 
boiling. Let the solution stand until the precipitate set- 
tles, and test the supernatant liquid with a drop of barium 
hydroxide solution to be sure that precipitation is com- 
plete. When the precipitation is complete, filter and wash 
the residue thoroughly with hot water. AYhile the solution 
is boiling add ammonium hydroxide and ammonium car- 
bonate to precipitate the barium. Allow the solution to 
stand for a short time on a water bath, filter, wash the pre- 
cipitate thoroughly with hot water, and evaporate filtrate 
and washings to dryness. Expel the ammonium salts by 
heating at a low red heat as before, dissolve the residue 
in about 20 cc. of water, add about 2 cc. of ammonium 

* If desired, potash can be determined by optional methods (Exps. 
Nos. 34 a, 34&). 

[47] 



•5-: 



hydroxide and a drop of ammonium carbonate solution, 
let stand on a water bath for a few minutes, and filter 
into an evaporating dish. Evaporate filtrate and washings 
nearly to dryness, add 1 cc. of dilute H^SO^ (1 : 1), evap- 
orate to dryness, and ignite to whiteness. As all the 
potassium is in the form of sulphate, no loss need be 
apprehended by volatilization of potash, and a full red 
heat must be mamtained until the residue is perfectly 
white. Dissolve the residue in about 15 cc. of water, add 
a few drops of hydrochloric acid, and platinum solution 
(H^PtClg) * in slight excess (avoid the use of too large 
an excess, as the reagent is very expensive). Evaporate on 
a water bath to a thick paste, and treat the residue with 
80 per cent alcohol (sp. gr. 0.8645). If enough platinum 
solution has been added to precipitate all the potassium, 
the alcoholic solution will be slightly colored. If the alco- 
hol is not slightly colored, it must be evaporated off, the 
precipitate redissolved in water containing a few drops of 
HCl, more platinum solution added, and again evaporated 
to a thick paste and treated with alcoliol as before. If the 
alcoholic solution is not colored, owmg to an excess of 
platinum solution, do not add more platinum solution 
directly to the alcoholic solution, but evaporate off the 
alcohol first. Also avoid the absorption of ammonia by the 
solution. After the precipitate is treated with the 80 per 
cent alcohol, filter into a properly prepared and iveighed 
Gooch crucible, wash thoroughly with 80 per cent alcohol, 
then with 10 cc. of the special ammonium chloride solu- 
tion t to remove impurities. Repeat washing with the 
special ammonium chloride solution about five times, and 

* Prepared according to directions on page 90. 
t Prepared according to directions on page 90. 

[48] 



again wash thoroughly with 80 per cent alcohol. Dry the 
precipitate for thirty minutes at the temperature of boil- 
ing water, cool in desiccator, and weigh. The precipitate is 
potassium platinic chloride (K^PtClJ, and should be per- 
fectly soluble in water (which gives a means of checking 
the results if desired). For the conversion of potassium 
platinic chloride to potassium oxide (}^fi^ use the factor 
0.1941. Calculate and report the percentage of potash 
(K^O) in the soil soluble in the acid solution. (Save all 
filtrates and potassium platinic chloride precipitates so as 
to recover the platinum.) 

Questions 

1. How is the factor 0.1941 obtained ? 2. Write equations 
illustrating each step in the determination. 

Experiment No. 34 a (Optional Method) 

DETEKMINATION OF POTASH (K.fi) IN SOIL SOLUTION BY 
VOLUMETllIC METHOD * 

Measure out, with a burette or pipette, two 100 cc. 
portions of Solution A, place in beal^ers, heat to boiling, 
add NH^OH, drop hy drop, until the solution is strongly 
alkaline, and a few cubic centimeters of ammonium oxalate 
solution. Cover the beaker and boil the solution for about 
one minute ; if no ammonia is given off (detect by smelling), 
more is added, drop by drop, until it can be detected. Do 
not allow the precipitate to settle, but stir and filter imme- 
diately while hot, washing it thoroughly with hot water. 

* Most of the points in the manipulation were taken directly from a 
method suggested by O. M. Shedd for the determination of total potas- 
sium in soils, Journal of Industrial and Engineering Chemistry, Vol. I, 
No. 5, May, 1909. 

[49] 



Evaporate the filtrate and washings nearly to dryness 
in an evaporating dish, add 1 cc. of dilute H^SO^ (1 : 1), 
evaporate to dryness, and ignite to whiteness by maintain- 
ing a full red heat until the residue is perfectly white. 

Dissolve the residue in hot water, filter if necessary to 
remove any insoluble material, acidify the clear solution 
slightly with acetic acid, and evaporate to a volume of 
about 10 or 15 cc* Ten cubic centimeters or a liberal 
excess of the cobaltinitrite reagent, prepared according to 
Adie and Wood, are added slowly, so that the precipitate 
may not be too finely divided, and the liquid evaporated off 
on the water bath to a sirupy consistency, becoming solid 
on cooling. It is important not to heat longer than is 
necessary. After cooling, the soluble matters are dissolved 
in about 25 cc. of cold water (which should give a brown 
solution, showing excess of reagent), the solution decanted 
through a carefully prepared Gooch crucible,''' and this 
operation repeated until the dish and any precipitate re- 
maining in it have been thoroughly washed. t Be sure that 
all the precipitate is completely removed from the dish. 
After washing the filter, the contents of the crucible (the 
asbestos with the precipitate) are transferred to a 500 cc. 
beaker and well broken up by stirring with a glass rod 
in a little water. If any of the precipitate adheres to the 
Gooch crucible so that it cannot be washed off, the cruci- 
ble also is to be put into the dish. A measured excess 

* When the reagent is added to a dilute solution, it is decomposed 
before the potassium salt is precipitated. In small volumes this does 
not happen. 

t The asbestos pulp for making the filter should be just fine enough 
to hold the precipitate and be free from very fine particles. 

t A half-saturated solution of common salt may be used instead of 
water if there is trouble in filtering the precipitate. 

[50] 



of standard potassium permanganate solution * (usually 
20-40 CO.) is now run in, and the whole diluted to about 
eight or ten times the volume of permanganate added, the 
dish covered, and its contents heated to boihng over a 
free flame or on a hot plate, with frequent stirring for 
about ten minutes, or until the potassium cobaltinitrite 
is oxidized completely. It has been found that the oxida- 
tion requires a somewhat longer time than the five to eight 
minutes recommended by Drushel, apparently because it is 
hard to separate the yellow potassium precipitate from the 
asbestos so that the permanganate can come in contact with 
it. When the oxidation is complete — as indicated by the 
darkening of the solution and the separation of the man- 
ganese hydroxide — about 15 cc. of dilute sulphuric acid 
(1 : 7) are added and allowed to act three or four minutes 
to favor oxidation of the last traces of cobaltinitrite. t A 
measured excess of the standard oxalic acid t containing 
50 cc. of concentrated sulphuric acid to the liter is then 
run in, and the liquid kept at the same temperature until 
all the manganic hydroxide has been dissolved and the 
solution is colorless. At this point it will be seen by the 
absence or presence of the yellow potassium compound 
whether the oxidation of the cobaltinitrite precipitate was 
complete. The excess of oxalic acid is now titrated with 
the standard permanganate solution. § The total volume 
of permanganate solution used, less that equivalent to the 
oxalic acid added, gives the amount used up in oxidizing 

* See Experiment No. 15 (approximate N/10 solution). 

t The sulphuric acid is not to be added at first, along with the per- 
manganate, as the action would be very rapid and some cobaltinitrite 
might escape oxidation. 

t Prepared according to directions on page 90, 

§ See Experiment No. 15. 

[51] 



the cobaltinitrite ; and this, multiplied by the appropriate 
factor, gives the weight of potassium obtained. One cubic 
centimeter of N/10 permanganate solution is equivalent 
to 0.000711 g. of K, or 0.000856 g. of Kp. If the potas- 
sium permanganate solution used for the titration is not 
exactly N/10, then it is necessary to calculate the appro- 
priate factor to be used. It is also necessary to carry out 
a blank experiment, under the same conditions as the 
analysis, using the same quantities of the reagents, and to 
subtract the small amount of permanganate solution con- 
sumed from that found in the analysis. From the results 
obtained, calculate and report the percentage of potash 
(K O) in the sample of soil soluble in the acid solution. 

Question 

How is the factor for the K equivalent of 1 cc. N/10 KMO^ 
obtained ? 

Experiment No. 34 & (Optional Method) 

DETERMINATION OF POTASH (K^O) IN SOIL SOLUTION BY 
THE USE OF PLATINUM SOLUTION* 

Measure out, with a burette or pipette, two 100 cc. 
portions of Solution A into glazed porcelain evaporating 
dishes, add 10 cc. concentrated C. P. hydrochloric acid, 
and evaporate to dryness. Take up with 10 to 15 cc. 
of distilled water, add about 5 cc. of platinum chloride 
solution and 2 or 3 cc. of hydrochloric acid, and evaporate 
to dryness or to a thick paste on a water bath. Remove 
the dish from the water bath and let stand until it is 

* This method is a modification of the method proposed by C. C. Moore, 
Journal of American Chemical Society, Vol. XX (1898), p. 340, and of the 
method used in the laboratories of the Texas Experiment Station. 

[52] 



perfectly cold. Add from 10 to 30 cc. of " acid alcohol," * 
according to the amount of precipitate in the dish. All 
other materials beside the precipitate of potassium platinic 
chloride should be completely dissolved. If there is heat 
evolved when the acid alcohol is added, more alcohol is 
added to cool the solution, as this reaction often forms a 
white insoluble substance which would ruin the results. 
If enough platinum solution has been added to precipitate 
all the potassium, the alcoholic solution will be slightly 
colored. If the alcohol is not slightly colored, it has to 
be evaporated off, the precipitate redissolved in distilled 
water containing a few drops of hydrochloric acid, more 
platinum solution added, and again evaporated to a thick 
paste and the solution treated Avith acid alcohol, as before. 
If the alcoholic solution is not colored, owing to an excess 
of platinum solution, do not add more platinum solution 
directly to the alcoholic solution, but evaporate off the 
alcohol first. After the precipitate is treated with acid 
alcohol, filter by decantation into a properly prepared and 
weighed Gooch crucible ; wash once with acid alcohol, then 
with 95 per cent alcohol until the alcohol wash does not 
dissolve any more colored material of any kind; pour the 
washings through the crucible each time, but leave the 
precipitate in the evaporatmg dish as far as possible. Add 
10 cc. of special ammonium chloride solution t to the pre- 
cipitate in the dish, let stand a few minutes so as to 
dissolve impurities, and pour off the solution through the 
Gooch crucible. Repeat the washing with the special 
ammonium chloride solution about five times and again 

* 10 cc. of concentrated C. P. hydrochloric acid solution added to 
100 cc. of 95 per cent alcohol. 

t Prepared according to directions on page 90. 

[53] 



wash thoroughly with 95 per cent alcohol. Transfer the 
potassium platinic chloride precipitate from the dish to the 
Gooch crucible by the use of 95 per cent alcohol, washing 
the side of the crucible carefully so as to remove any 
adhering solution of ammonium chloride. Dry the pre- 
cipitate for thirty minutes at the temperature of boiling 
water, cool in desiccator, and weigh. The precipitate is 
potassium platinic chloride (K^P^^Ilg), and should be per- 
fectly soluble in water (which gives a means of checking 
the results if desired). For the conversion of platinic 
chloride to potassium oxide (K„()) use the factor 0.1941. 
Calculate and report the percentage of potash (K^O) in 
the soil soluble in the acid solution. (Save all filtrates and 
potassium platinic chloride precipitates so as to recover 
the platinum.) 

Note. " Available " phosphoric acid and potash in soils can be 
determined by digestion with 1 per cent citric acid (Dyer's method). 
Journal of American Chemical Society, Vol. LXVI (1894), p. 115 ; 
Lunge, Technical Methods of Chemical Analysis, Vol. I, p. 852. 



[54] 



PART lY 

ANALYSIS OF r^RTILIZEES 

Pkeparation of Sample of Fektilizer for 
Analysis * 

Grind the sample fine enough to pass through a sieve 
having circular perforations 1 mm. in diameter, and then 
mix thoroughly. Perform the grinding and sifting as rap- 
idly as possible to avoid loss or gain during the operation. 
After the sample is prepared and thoroughly mixed, it 
should be kept in a well-stoppered bottle. Enough sample 
should be prepared for all the determinations. 

Experiment No. 35 

determination of moisture in fertilizer 

Weigh out exactly 2 g. of the fertilizer in a weighed 
watch glass and dry for three hours at the temperature of 
boiling water ; cool in desiccator, and weigh rapidly. Heat 
again at intervals of one-half hour until the material ceases 
to lose weight. IMake duplicate determinations. Calculate 
and report the percentage of moisture in the sample of 
fertilizer. 

* Bulletin No. 107 (Revised), Bureau of Chemistry, United States 
Department of Agriculture. 

[55] 



Experiment No. 36 

PREPARATION OF A STANDARD NaOH SOLUTION FOR 
PHOSPHORIC ACID (PgOg) DETERMINATION 

Make up a solution (500 cc.) of sodium h3'droxide 
(NaOH) so that 10 cc. of this solution should neutralize 
16.2 cc. of an exactly N/5 HCl solution. If your standard 
hydrochloric acid solution is not exactly N/5, then calcu- 
late the number of cubic centimeters of your HCl solution 



mk',^ «^i^S^; 




i^^HiiSli^ 



COMBINATION ELECTKIC WATER BATH AND HOT PLATE 

which will be equivaleyit to 16.2 cc. of an exactly N/5 HCl 
solution. Standardize the NaOH solution so that 10 cc. of 
it will exactly neutralize the calculated number of cubic 
centimeters of your standard acid. One cubic centimeter 
of the NaOH solution will then be equivalent to .001 g. 
of phosphoric acid (P^O^). 

[56] 



Question 

Show that 1 cc. of the NaOH solution is equivalent to 
.001 g. of Pp,. 

Note. For equation see Experiment No. 33 a. 

Experiment No. 37 

DETEEMINATION OF TOTAL PHOSPHORIC ACID (P^O^) 
IN FERTILIZER 

Weigh out 2 g. of the sample of fertilizer and place it 

in a beaker with 15 to 20 cc. of concentrated hydrochloric 

acid and from 3 to 10 cc. of concentrated nitric acid, and 

digest from 20 to 30 minntes under the hood. After the 

solution is complete, cool, add 25 cc. of distilled water, 

filter, and wash the residue thoroughly, allowing the wasii- 

ing-s and the original solution to run into a 250 cc. measur- 
es o 

m(/ flask. INIake up to the mark with distilled water, 
stopper the flask, and shake thoroughly. Measure out, 
with a burette or pipette, two 25 cc. portions into beakers 
for analysis, and to each portion add 25 cc. of distilled 
water. Make alkaline with NH^OH, adding 10 cc. in 
excess, and then sli(jhtlij acid with HNO^ (1 : 1), using a 
small piece of litmus paper m the solution as indicator. 
Avoid much excess of HNOg. Warm the solution to the 
temperature of 60° to 65° C. by standing the beakers in 
a pan containing warm water. After the solution has 
reached the required temperature add 30 cc. of ammonium 
molybdate solution ; stir, and let stand for fifteen mmutes 
in the warm water at 60° to 65° C. Filter at once and 
wash twice with water by decantation^ by pouring the solu- 
tion through the filter, using 25 to 30 cc. of water each 
time, agitating the precipitate thoroughly, and allowing it 

[57] 



to settle. Transfer to the filter paper and wash with cold 
water until washings are free from acid. (Test by means 
of litmus paper.) Transfer the filter paper containing the 
precipitate back into the beaker in which it was precipi- 
tated. From the burette add your standard NaOH solu- 
tion (prepared for the l^fi^ determination) until the yellow 
precipitate is completely/ dissolved. Add about 25 cc. of dis- 
tilled water and a few drops of phenolphthalein indicator. 

1. Should the solution be colorless with the indicator 
added, continue the addition of NaOH solution until a 
permanent pink color is obtained; that is, the end-point 
is reached. 

2. Should the solution be colored after tlie indicator is 
added, that is, alkaline, titrate with your standard HCl 
solution until the color is discharged, and then titrate 
with your standard NaOH solution until the end-point is 
obtained. 

In either case the total amount of NaOH used to dis- 
solve mid titrate the yellow precipitate and also the total 
amount of standard HCl used should be recorded. From 
the data obtained calculate and report the percentage of 
phosphoric acid (P^O^) in the sample of fertilizer. 

Questions 

1. Give the reason for each step in the determination and 
write equations for the reactions. 2. Define raw rock phos- 
phate, basic slag, acid phosphate, water-soluble phosphoric 
acid, reverted phosphoric acid, insoluble phosphoric acid, and 
give their chemical compositions and methods of preparation. 



[58] 



Experiment No. 38 

DETERMINATION OF WATER-SOLUBLE PHOSPHORIC 
ACID (P2O5) IN FERTILIZER 

Weigh out 2 g. of the sample, place it on a 9 cm. filter 
paper, and leach with successive small portions of distilled 
water into a 250 cc. measuring flask (allowing each por- 
tion of water to run through before adding more) until 
the filtrate measures nearly 250 cc. If the filtrate is turbid, 
add a few drops of concentrated IIN^O^. Make up to the 
mark with distilled water and shake the solution thor- 
oughly. JVIeasure out, with burette or pipette, two 25 cc. 
portions into beakers and proceed as in Experiment No. 37. 
Save the residue in the filter paper for Exj^eriment No. 39. 



Experiment No. 39 

DETERMINATION OF CITRATE-SOLUBLE PHOSPHORIC 
ACID (P2O5) IN FERTILIZER 

Heat 100 cc. of strictly neutral ammonium citrate solu- 
tion * (sp. gr. 1.09) to G5°C. in a 200 to 300 cc. Erlen- 
meyer flask placed in a warm water bath, keeping the flask 
loosely stoppered. When the citrate solution has reached 
the temperature of Q^° C, drop into it the filter paper 
containing the leached residue from the water-soluble phos- 
phoric acid determination (Exp. No. 38), close tightly 
with a smooth rubber stopper, and shake violently until 
the filter paper is reduced to a pulp. Place the flask in the 
bath, and maintain it at such a temperature (about 67° C.) 

* Prepared according to directions on page 91. 

[59] 



that the contents of the flask will stand exactly at 65° C. 
Shake the flask every five minutes. At the expiration 
of exactly thirty minutes from the time the filter with con- 
tents was introduced, remove the flask from the bath and 
filter as rapidly as possible. Wash the residue and flask 
tliorouglily with distilled water heated to the temperature 
of 65° C. Return the filter with contents to the Erlen- 
meyer flask, add 30 cc. of concentrated HNO^ and 10 cc. 
of concentrated HCl, and digest under the hood until 
phosphates are dissolved ; that is, about twenty or thirty 
minutes. Dilute with 50 cc. of distilled water, and filter 
into a 250 cc. measuring flask, washmg the residue thor- 
oughly. Make up with distilled water to the mark, shake 
thoroughly, and measure out, with burette or pipette, two 
25 cc. portions into two beakers. Then proceed as in Ex- 
periment No. 37. The total phosphoric acid minus the sum 
of the water-soluble and citrate-insoluble gives the citrate- 
soluble phosphoric acid. Calculate and report the percent- 
age of citrate-insoluble and citrate-soluble phosphoric acid 
(P^Og) m the sample of fertilizer. 

Questions 

1. Give the formulas for uiolybdic acid, ammonium molyb- 
date, ammonium phosphomolybdate, and citrate-soluble phos- 
phoric acid. 2. Write the equation for the reaction of 
ammonium phosphomolybdate and ISTaOH. 3. Discuss the solu- 
bility of monocalcium, diealcium, and tricalcium phosphate. 
4. Define " available " phosphoric acid. 



[60] 



Experiment No. 40 

DETERMINATION OF POTASH (K.^O) IN A MIXED FERTI- 
LIZER BY THE USE OF PLATINUM SOLUTION* 

Boil 5 g. of the fertilizer sample with 300 cc. of distilled 
water thirty minutes. Add to the hot solution a slight 
excess of NH OH and then sufficient ammonium oxalate 

4 

solution to precipitate all the lime present. Cool, dilute 
to 500 cc. with distilled water in a measuring flask, shake 
thoroughly, and filter through a chy filter. Evaporate in 
an evaporatmg dish 100 cc. of the solution (measured 
exactly and corresponding to 1 g. of the sample) nearly 
to dryness, add 1 cc. of dilute sulphuric acid (1 : 1), evap- 
orate to dryness (being careful not to lose anything by 
spattering), and ignite to whiteness. As all the potas- 
sium is in the form of sulphate, no loss need be appre- 
hended by volatilization of potash, and a full red heat 
must be maintained until the residue is perfectly white. 
Dissolve the residue in hot water and filter if any insoluble 
material remains. Add to the clear solution a few drops 
of HCl, and platinum solution (H2PtClg)t in slight excess. 
Evaporate on a water bath to a thick paste and treat 
the residue with 80 per cent alcohol (sp. gr. 0.8645). If 
enough platinum solution has been added to precipitate all 
the potassium, the alcoholic solution will be slightly colored. 
If the alcohol added to the residue is not slightly colored, 
the alcohol has to be evaporated off, residue redissolved 
in water containing a few drops of HCl, more platinum 

* Potash can be determined by optional method (Exp. No. 40 a). 
t Prepared according to directions on page 90. 

[61] 



solution added, and the solution again evaporated to a 
thick paste and treated with alcohol. Do not add more 
platmum solution to the alcoholic solution before evapo- 
rating off the alcohol. Avoid the absorption of ammonia by 
the solution. After the residue is treated with 80 per cent 
alcohol, filter into a properly prepared and treighed Gooch 
crucible and wash the precipitate thoroughly with 80 per 
cent alcohol, then with 10 cc. of the special ammonium 
chloride solution,* to remove impurities. Repeat washing 
with 10 cc. portions of special ammonium chloride solution 
about five times, and agam wash thoroughly w^ith the alco- 
holic solution. Dry the precipitate for thirty minutes at 
the temperature of boiling water, cool in desiccator, and 
Aveigli. The precipitate is potassium platinic chloride 
(KgPtClg) and should be perfectly soluble in water (which 
gives a means of checking the results if desired). For 
the conversion of potassium platinic chloride (K^PtClg) to 
potassium oxide (K^O) use the factor 0.1941. From data 
obtained, calculate and report the percentage of potash 
(K O) in the sample of fertilizer. (Save all the filtrates 
and potassium platinic chloride precipitates so as to 
recover the platinum.) 

Experiment No. 40 a (Optional Method) 

DETERMINATION OF POTASH (K.^O) IN MIXED FERTILIZER 
BY VOLUMETRIC METHOD 

Measure ont into evaporating dishes, with a burette or 
pipette, two 25 cc. portions of the filtered potassium solu- 
tion prepared in Experiment No. 40. Evaporate each por- 
tion nearly to dryness in an evaporating dish, add 1 cc. 

* Prepared according to directions on page 90. 

[62] 



of dilute sulphuric acid (1 : 1), evaporate to dryness, and 
ignite to whiteness by maintaining a full red heat until 
the residue is perfectly white. Dissolve the residue in hot 
water, filter if any remains undissolved, acidify the clear 
solution slightly with acetic acid, and proceed in the same 
manner as in Experiment No. 34 a. From data obtained 
calculate and report the percentage of potash (K^O) in 
the sample of fertilizer. 

Experiment No. 41 

DETERMINATION OF NITROGEN IN FERTILIZERS 
(NITRATES PRESENT) 

Weigh out exactly 1 to 2 g. of the sample and transfer 
to an 800 cc. Kjeldahl flask. Add 30 cc. salicylic acid 
solution* and 5 g. of sodium thiosulphate. Heat over a 
low flame until all danger of frothing has passed, cool, 
and then add about 10 g. of K^SO^ and about .5 g. copper 
sulphate (CuSO^ . 5 H^O). Continue the digestion until 
the material is completely oxidized. Make the distillation 
and titration as given in Experiment No. 19. Make 
duplicate determinations. From data obtained, calculate 
and report the percentage of nitrogen in the sample of 
fertilizer. 

Questions 

1. Explain the use of salicylic acid and sodium thiosulphate. 
Write equations illustrating. 2. Explain the other steps in the 
determination. 

* Prepared according to directions on page 91. 



[6.3] 



PART y 

ANALYSIS OF INSECTICIDE AND FUNGICIDE 
Experiment No. 42 

PREPARATION AND STANDARDIZATION OF SOLUTION 

POR DETERMINATION OF ARSENIOUS OXIDE (ASgOg) 

IN PARIS GREEN 

Starch solution for iyidicator. Place 1 g. of starch in 
10 cc. of cold distilled water to separate the granules, and 
then pour this mixture into 100 cc. of boiling water. Boil 
for five minutes, stirring continuously. 

Standard iodine solution. Dissolve about 3.5 g. of iodine 
in 200 cc. of distilled water in which has been dissolved 
from 8 to 10 g. of pure potassium iodide (KI). Dilute 
to a volume of 500 cc. with distilled water and shake 
thoroughly. 

Before standardizing be sure that all the iodine is in 
solution. Dissolve exactly 1 g. of pure arsenious oxide 
(As O ) m 50 cc. of HCl (1:1), heating rapidly if neces- 
sary to bring all the arsenic into solution. (Do not boil 
the solution.') Cool and make up to a volume of 250 cc. 
in a measuring flask. Perform the titration as follows: 
Measure out, with a burette or pipette, two portions of 
25 cc. of the arsenious oxide (As^O^) solution into porce- 
1am evaporating dishes (about 6 in. m diameter) or into 

[64] 



large beakers, add about 300 cc. of distilled water, and 
sodium bicarbonate (NaHCOg) in slight excess. Add the 
iodine solution from a burette, using the starch solution 
as an indicator. The titration is complete when you obtain 
the first permanent blue color. Make at least two titra- 
tions. Calculate the strength of the iodine solution in 
terms of arsenious oxide (As^Og). 

Question 

Why should the hydrochloric acid solution of arsenious 
oxide not be boiled ? 

Experiment No. 43 

DETERMINATION OF TOTAL ARSENIOUS OXIDE (AS2O3) 
IN PARIS GREEN 

To determine the total arsenious oxide in Paris green 
use 2 g. and proceed exactly as with the arsenious oxide 
in the standardization of iodine solution (Exp. No. 42). 
Make duplicate determmations. Calculate and report the 
percentage of arsenious oxide (As^O^) in the sample of 
Paris green. 

Questions 

1. Is Paris green a compound or a mixture ? 2. If a com- 
pound, what is its formula ? 3. To what is the As^Og oxidized 
by the iodine ? 4. Give equations for the reaction. 5. How 
much As^Og can Paris green contain and still be safe as an 
insecticide ? 6. Give a simple test for the purity of Paris 
green. 



[65] 



Experiment No. 44 

DETERMINATION OF WATER-SOLUBLE ARSENIOUS OXIDE 
(AS2O3) IN PARIS GREEN 

Place 1 g. of Paris green (weighed exactly) in a large 
flask with exactly 500 cc. of distilled water (previously 
boiled to expel carbon dioxide and then cooled to room 
temperature). Stopper the flask, shake thoroughly, and 
let stand for one week, shakmg as often as convenient. 
At the end of this time filter the solution through a dry 
filter. Dilute 100 cc. of the filtrate with 100 cc. of dis- 
tilled water, add sodium bicarbonate (NaHCO^) in slight 
excess, and titrate with your standard iodine sohition in 
the same manner as m Experiment No. 42, using the 
starch solution as indicator. Make duplicate titrations. 
Calculate and report the percentage of water-soluble 
arsenious oxide (As^Og) in the sample of Paris green. 

Analysis of Lead Arsenate * 

Preparation of saynple. If the sample is in the form of 
a paste (as it usually is), dry the whole sample to constant 
weight at the temperature of boiling water and record the 
results as total moisture. Grind the dry sample (which 
will gain a small amount of moisture during grinding) 
to a fine powder and determine the various constituents 
as follows: 

* These methods are modifications of methods proposed by Haywood, 
Bulletin No. 105, Bureau of Chemistry, United States Department of 
Agriculture (1907), p. 165. 

[66] 



Experiment No. 45 

DETERMINATION OF MOISTURE IN LEAD ARSENATE 

Heat 2 g. of the sample in the water oven at the tem- 
perature of boiling water for eight hours or in the hot- 
air oven at 110° C. for from five to six hours or till 
constant weight is obtained. Make duplicate determina- 
tions. Calculate and report the percentage of moisture 
in the sample of lead arsenate. 

Experiment No. 46 

DETERMINATION OF TOTAL LEAD OXIDE IN LEAD 
ARSENATE 

Dissolve 2 g. of the sample in about 80 cc. of water and 
15 cc. of concentrated nitric acid on the steam or water 
bath ; transfer the solution to a 250 cc. measuring flask 
and make up to the mark. To 50 cc. of the solution add 
3 cc. of concentrated sulphuric acid ; evaporate on the 
steam bath to a sirupy consistency and then on a hot 
plate till white fumes appear and all nitric acid has been 
driven off. Add 50 cc. of water and 100 cc. of 95 per cent 
alcohol, let stand for several hours, and filter off the 
supernatant liquid ; wash about ten times with acidified 
alcohol (water 100 parts, 95 per cent alcohol 200 parts, 
and concentrated sulphuric acid 3 parts) and then with 
95 per cent alcohol* till free from sulphuric acid. Dry, 
transfer as much as possible of the precipitate from the 
paper into a weighed crucible, and ignite at a low red 

* Prepared according to directions on page 92. 

[67] 



heat. Burn the paper in a separate porcelain crucible, and 
treat the residue first with a little nitric acid, which is 
afterwards evaporated off, and then with a drop or two 
of sulphuric acid. Ignite, weigh, and add this weight to 
the weight of the precipitate previously removed from the 
paper for the amount of the lead sulphate. Calculate 
and report the percentage of lead oxide m the sample of 
lead arsenate. 

Question 

Write equations for the chemistry of each step in the 
determination. 

Experiment No. 47 

DETERMINATION OF WATER-SOLUBLE LEAD OXIDE IN 
LEAD ARSENATE 

Weigh out 2 g. of the lead arsenate, place in a flask 
with 2000 cc. of carbon-dioxide-free water, and let stand 
for a week, shaking as often as convenient (eight times 
a day if possible). Filter through a dry filter and use 
aliquots (200 to 400 cc.) of this solution for determin- 
ing soluble lead oxide and arsenic oxide (As^O^) ; deter- 
mine lead as described in Experiment No. 46 for total 
lead oxide, using the same relative proportions of sul- 
phuric acid, water, and alcohol, but keeping the volume 
as small as possible. ]\Iake duplicate determmations. Cal- 
culate and report the percentage of water-soluble lead 
oxide m the sample of lead arsenate. 



[68] 



Experiment No. 48 

DETERMINATION OF TOTAL ARSENIC OXIDE (AS2O5) IN 
LEAD ARSENATE 

Transfer 100 cc. of the nitric acid solution of the sample, 
prepared as in the determination of lead (Exp. No. 46), 
to a porcelain dish, add 6 cc. of concentrated sulphuric 
acid, evaporate on the water bath to a sirupy consist- 
ency and then on a hot plate until the appearance of 
white fumes of sulphuric acid. Wash into a 100 cc. flask 
with water, make up to the mark with distilled water, 
filter through a dry filter, and use 50 cc. aliquot parts for 
further work. Transfer this to an Erlenmeyer flask of 
400 cc. capacity, add 4 cc. of concentrated sulphuric acid 
and 1 g. of potassium iodide, dilute to about 100 cc, and 
boil until the volume is reduced to about 40 cc. Cool the 
solution under running water, dilute to about 300 cc, and 
exactly use up the iodine set free and still remaining in the 
solution w4th a few drops of approximately tenth-normal 
sodium thiosulphate solution. Be careful that an excess of 
sodium thiosulphate is not used. Wash the mixture into 
a large beaker, make alkalme with sodium carbonate, and 
slightly acidify with dilute sulphuric acid, using up all 
the sodium carbonate ; then make alkaline with an excess 
of sodium bicarbonate. Titrate the solution with your 
standard iodine solution until a blue color appears, using 
the starch solution as indicator. Calculate and report the 
percentage of arsenic oxide (As^O^) in the sample of lead 
arsenate. 

[69] 



Questions 

1. Discuss the commercial preparation of lead arsenate and 
varieties. 2. Name the desirable properties of an insecticide. 
3. Write equations for the chemistry of each step in the 
determination. 

Experiment No. 49 

DETERMINATION OF WATER-SOLUBLE ARSENIC OXIDE 
(AS2O5) IN LEAD ARSENATE 

For this determination use 200 to 400 cc. of the water 
extract obtained under the determination of soluble lead 
oxide (Exp. No. 47). Add 0.5 cc. of sulphuric acid and 
evaporate to a sirupy consistency, then heat on a hot plate 
until white fumes appear. Add a very small amount of 
distilled water, and filter through a small iilter paper to 
remove the lead, using as little wash water as possible. 
Place this filtrate in an Erlenmeyer flask, and determine 
arsenic, as described above, for total arsenic oxide, using 
the same amount of reagents and the same dilutions. Cal- 
culate and report the percentage of Avater-soluble arsenic 
oxide (As.^Og) in the sample of lead arsenate. 

Experiment No. 50 

TESTING BORDEAUX MIXTURE FOR SOLUBLE COPPER 

Take a small piece of quicklime (CaO) and slake it 
with water. Weigh out on the rough balance about 5 g. 
of copper sulphate (CuSO^ • 5 H^O) and dissolve in about 
100 cc. of water. Add the milk of lime to the copper 
sulphate solution until you cannot obtain a test with 
potassium ferrocyanide (K^Fe(CN)g).* (The test for 
* Prepared according to directions on page 92. 

[70] 



soluble copper should be made by using small filtered por- 
tions taken from the original mixture.) This is known as 
Bordeaux mixture. Take a portion of the mixture, dilute 
it with water, and pass carbon dioxide mto it for about 
fifteen minutes. Again test the solution for soluble copper. 

Questions 

1. Explain your results. 2. Also make the test for soluble 
copper by adding a drop of dilute ammonia to the clear solu- 
tion, noting the blue copper hydroxide. Add more ammonia 
and observe the soluble blue compound. 3. How does the 
carbon dioxide of the air cause bad effects with Bordeaux 
mixture ? 4. How could you prevent it ? 5. Discuss the 
composition of Bordeaux mixture and the killing of foliage by 
its use as a spray. 6. With what insecticides can it be used ? 



[71] 



PART YI 

ANALYSIS OF MILK 
Experiment No. 51 

DETERMINATION OF SPECIFIC GRAVITY OF MILK 

The sample of milk is thoroughly mixed and poured 
into a cylinder or hydrometer jar. Determine iirst the 
temperature of the milk and then, by means of a hy- 
drometer or lactometer, determine the specific gravity. 
The hydrometer or lactometer should be gently lowered 
into the milk and the reading observed from the top of 
the meniscus. The temperature of the milk should be 
adjusted to 15.5° C. before the readmg is made, or the 
correction for the temperature should be made so as to 
record the specific gravity reading at the temperature of 
15.5° C. or 60° F. The Quevenne and New York Board 
of Health lactometers are used to the largest extent for 
this determination. To prevent the milk from souring 
before the other determinations are made, add 1 cc. of 
formalin (40 per cent solution of formaldehyde) to one 
pint of the milk, and keep the bottle stoppered. 

Questions 

1. What is specific gravity ? 2. Name four ways of deter- 
mining specific gravity of a liquid. 3. Explain the effect of 

[72] 



watering and skimming (and the two combined) upon the 
specific gravity. 

References 

Leach. Food Inspection and Analysis. 

Richmond. Dairy Chemistry. 

Van Slyke. Modern Methods of Testing Milk and Milk Products. 

Wiley. Agricultural Analysis, Vol. III. 



Experiment No. 52 

DETERMINATION OF TOTAL SOLIDS IN MILK 

Measure out, with a burette or pipette, 10 cc. of milk 
of known specific gravity mto a tared flat-bottomed dish of 
not less than 5 cm. diameter. Evaporate to dryness on 
a water bath, and dry in water oven for thi^ee hours at 
the temperature of boiling water. Cool in desiccator and 
weigh rapidly. Heat again at intervals of one-half hour 
until the material ceases to lose weight. Make duplicate 
determmations. Calculate and report the percentage of 
total solids in the sample of milk. 

Questions 

1. What does the total solids of milk contain ? 2. The milk 
residne should be nearly pure white (a brownish color shows 
decomposition). Explain. 2. What effect would the souring 
of milk have on the content of the total solids in the milk? 
Explain. 

Experiment No. 53 

DETERMINATION OF ASH IN MILK 

Measure out, with a burette or pipette, two 25 cc. por- 
tions of milk into weighed porcelam dishes. Add 5 cc. of 
concentrated HNO^, evaporate to dryness, and ignite at 

[78] 



I 



a temperature just below redness until the ash is free of 
carbon. Cool in desiccator and weigh. Make duplicate 
determinations. Calculate and report the percentage of 
ash in the sample. 

Question 

What does the ash of milk contain ? 

Experiment No. 54 

DETERMINATION OF FAT IN MILK BY THE WERNER- 
SCHMIDT METHOD 

Transfer 10 cc. of milk, measured accurately^ to a large 
test tube (50 cc. capacity), add 10 cc. of concentrated 
HCl, cork tightly, shake thoroughly, and heat in a water 
bath for about ten minutes, with frequent shaking, until 
the liquid is of a deep-brown color. The heating must 
not be continued too long. Cool the tube thoroughly 
in a stream of water, add about 30 cc. of ether, and 
shake vigorously. Allow to stand until the ether layer, 
which contains the fat, has separated out. Transfer as 
much as possible of the ether layer, without disturbing 
the other layer, to a weighed flask (this may con- 
veniently be done by closing the test tube with a cork 
provided with small glass tubes similar to a wash bottle, 
the larger tube adapted to slide up and down in the 
cork and turned up slightly at the bottom. When the 
ether layer is ready to be transferred to the flask, the slid- 
ing tube is arranged so that it terminates just above the 
division of the two layers, and the ether is then blown 
out into the weighed flask). Add 10 cc. of ether to the 
test tube and shake again. Transfer this ether layer to 
the weighed flask. In the same manner make two more 

[74] 



extractions and transfer the ether layer to the weighed 
flask as before. Evaporate off the ether in the weighed 
flask, dry at the temperature of boiling water until free 
of ether^ cool in desiccator, and weigh. Make duplicate 
determinations. Calculate and report the percentage of 
fat in the sample. 

Questions 

1. Name and describe two other methods for the determina- 
tion of fat in milk. 2. If the sample of milk is slightly churned, 
how would you proceed to determine the fat content ? 

Experiment No. 55 

DETERMINATION OF TOTAL PROTEIN (CASEIN AND 
ALBUMIN) IN MILK 

Measure out, with a burette or pipette, two 5 cc. portions 
of milk into Kjeldahl flasks, and proceed with the diges- 
tion, distillation, and titration as in Experiment No. 19. 
Multiply the percentage of nitrogen by 6.38 to obtain the 
percentage of total protem in milk. Calculate and report 
the percentage of total protem in the sample. 

Question 

How was the factor 6.38 obtained ? 

Experiment No. 56 

DETERMINATION OF CASEIN IN MILK 

Measure out, with a burette or pipette, two 10 cc. por- 
tions of milk into beakers, dilute with distilled water to a 
volume of 100 cc, heat to a temperature of 40° to 42° C, 
and add at once 1.5 cc. of an approximate 10 per cent 

[75] 



acetic acid solution. Stir with a rubber-tipped glass rod, 
or policeman, and let stand for about five minutes, then 
decant on filter, wash thoroughly with cold water by 
decantation (pouring the washings through the filter paper 
each time), and transfer precipitate completely to filter. 
The filtrate should be clear or very nearly so. If it is 
not clear when it is first run through, it should again be 
filtered through the same filter and washed as before. 
Transfer the filter paper and contents to Kjeldahl flasks 
and proceed with the digestion, distillation, and titration 
as in Experiment No. 19. Multiply the percentage of 
nitrogen by 6.38 to obtain the percentage of casein in the 
milk. Calculate and report the percentage of casein in the 
sample. 

Questions 

1. What is the federal standard for milk ? the state stand- 
ard ? 2. What is the composition of cow's milk ? 3. How does 
it differ from hmnan milk ? 4. How is cow's milk modified 
for infants ? 5. What facts shown by an analysis would influ- 
ence you to believe that a sample of milk had been skimmed ? 
watered ? skimmed and watered ? 6. To what is the acidity 
of milk due ? 7. What is the composition of Cheddar cheese ? 
8. Give the commercial uses of casein. 

Reference 

Leach. Food Inspection and Analysis (3d ed.), p. 160. 1914. 

Note. Casein may be determined by volumetric methods : 
AValker, Journal of Industrial and Engineering Chemistry, Vol. VI, 
pp. 131, 356 (1914) ; Hart, Journal of Biological Chemistry, Vol. VI, 
p. 445 (1909) ; Van Slyke and Bosworth, Technical Bulletin No. 10 
(1909), New York (Geneva) Experiment Station. 



[76] 



PART VII 

A BEIEF SANITAEY EXAMINATION OF WATER 
Experiment No. 57 

DETERMINATION OF TOTAL SOLIDS IN WATER 

Evaporate 200 cc. of water iii a small evaporating dish 
on a water bath (a portion of the total volume can be 
evaporated, then more added until the total amount is 
evaporated). Dry at 105° C. in an oven until weight is 
constant, cool in desiccator, and weigh. Calculate and 
report parts of total solids per million parts of water, also 
in terms of grains per gallon. 

Qualitative Analysis 

Test the residue for phosphates, chlorides, sulphates, 
iron, aluminium, magnesium, and calcium. 

Experiment No. 58 

DETERMINATION OF CHLORINE AS CHLORIDES IN WATER 

Measure out, with a pipette or burette, 50 cc. of water 
into each of two small beakers or evaporating dishes. 
Add from three to four drops of potassium chromate solu- 
tion (10 per cent) as an indicator, coloring the contents 
of each beaker exactly alike. Place the beakers on a white 
surface. Titrate the water in the beakers with standard 

[77] 



silver nitrate (AgNO^) solution. Add one drop at a time, 
and continue the titration with frequent agitation until 
the water shows the first tinge of red. Make duplicate 
determinations. If convenient, the titration should be per- 
formed under a yellow light or by wearing yellow-colored 
goggles. Calculate and report parts of chlorine and its 
equivalent in NaCl per million parts of water. 

Questions 

1. If the water contains over 5 parts of chlorine per 100,000 
parts of water, what is suspected ? Discuss. 2. What is the 
chlorine content of sea water ? 3. What is the sanitary 
significance of the chlorine content of water ? 4. Write equa- 
tions illustrating all reactions. 5. State the relative solubilities 
of silver chloride and silver chromate. 

Experiment No. 59 

DETECTION OF FREE AMMONIA IN WATER 

To 25 cc. of water in a tall test tube add 5 cc. of Ness- 
ler's reagent * and note the color. Only a faint yellow tinge 
should be visible. A deeper color or turbidity generally indi- 
cates animal contamination. Compare the treated sample 
with the untreated sample in a similar tube. The experi- 
ment can be made quantitatively by comparing the color 
of the sample with different samples of distilled water con- 
taining known amounts of ammonium chloride (NH^Cl). 

Questions 

1. Of what does Nessler's reagent consist ? 2. Define free 
and albuminoid ammonia. 3. How is albuminoid ammonia 
determined? 4. Discuss the significance of free and albumi- 
noid ammonia in water. 

* Prepared according to directions on page 92, 

[78] 



Experiment No. 60 

DETECTION OF NITRITES IN WATER 

Into a large test tube place a drop of HCl, 2 cc. 
sulphanilic acid* and equal volumes of naphthylamine 
hydrochloride,* and 50 cc. of the water under examination. 
If a red color is produced immediately or within twenty 
minutes, the presence of nitrites is assured. As a rule 
nitrites are not found in good water. Any water contain- 
ing nitrites should be suspected of being contaminated. 
Why ? The test tube should be corked to avoid contami- 
nation from laboratory atmosphere. 

Experiment No. 61 

DETECTION OF NITRATES IN WATER 

Evaporate 100 cc. of the sample to dryness in an 
evaporating dish over a water bath. Treat with 1 cc. of 
phenolsulphonic acid,* stirring thoroughly. Add 10 cc. of 
distilled water and half as much NH^OH. In the pres- 
ence of nitrates the characteristic color (yellow) of the 
ammonia salt of nitrophenol-sulphonic acid is formed. 
Nitrates are present in almost all natural waters. Why? 

* Prepared according to directions on page 93 or by a method proposed 
by Chamot, Pratt, and Redfield in an article entitled "A Study on the 
Phenolsulphuric Acid Method for the Determination of Nitrates in 
Water" (a modified phenolsulphuric acid method), Journal of American 
Chemical Society, Vol. XXXIII, No. 3 (1911). The reagent when prepared 
by the method recommended by Chamot, Pratt, and Redfield consists of 
the diacid with only traces of monoacids. This method is especially 
desirable when the reagent is to be used for quantitative work, as the 
method of preparation given in this manual yields a mixed product. 

[79] 



Experiment No. 62 

DETERMINATION OF ABSORBED OXYGEN IN WATER 

Place 100 cc. of water in a beaker and add 10 drops of 
H^SO^. Warm gently and add the standard solution 
(KMnO^), drop by drop (stirring constantly). As soon 
as the first tinge of pink appears, warm the beaker again 
and notice if the color is permanent. The first tinge of 
permanent pink denotes the end of the operation. The 
test should be limited to about fifteen minutes. 

This determination gives reliable information concern- 
ing the amount of organic contamination, but does not 
distinguish between that of vegetable and animal origin. 
If more than one grain per gallon is absorbed, the water 
is probably polluted. 

Experiment No. 63 

DETERMINATION OF TEMPORARY HARDNESS OR 
ALKALINITY OF WATER 

Titrate 100 cc. of water with your standard solution 
of HCl, using methyl orange or erythrosin and chloroform 
as indicator. Calculate and report results in parts of cal- 
cium carbonate (CaCOg) per 100,000 parts of water, 
giving the so-called degrees of hardness. If sodium or 
potassium carbonates are present, they will also react 
alkaline, but a correction for this error can be obtained 
by determining permanent hardness. 

Reference 

Olsen. Quantitative Chemical Analysis. 

[80] 



Questions 

1. What is hard water ? 2. Define permanent hardness 
and temporary hardness. 3. Give another way in which the 
hardness of water may be determined. 4. Give the essential 
determinations on water for the following purposes : (1) drink- 
ing, (2) boiler, (3) irrigation. 5. State the benefits derived 
from each. 6. Discuss the correction of undesirable properties 
of waters used for different purposes. 



[81] 



PART YIII 

APPENDIX 
BOOKS OF REFERENCE 

Airman, C. M. Milk, its Nature and Composition. 

Allen, A. H. Commercial Organic Analysis. 4 vols. 

Allyn, L. B. Elementary Applied Chemistry. 

Blyth, a. W. Foods, their Composition and Analysis. 

Bulletin No. 107 (Revised) (1907), Bureau of Chemistry, United 
States Department of Agriculture. " Methods of Analysis adopted 
by the Association of Official Agricultural Chemists." 

Bulletin No. 65 (1902), Bureau of Chemistry, United States Depart- 
ment of Agriculture. "Provisional Methods for the Analysis 
of Foods adopted by the Association of Official Agricultural 
Chemists." 

Chamot and Redfield. Analysis of Water. 

CoHN, Alfred I. Indicators and Test Papers. 

Evans, P. N. Course in Quantitative Chemical Analysis. 

FouLK, C. W. Notes on Quantitative Chemical Analysis. 

Frankland, Percy F. Agricultural Chemical Analysis. 

Fresenius. Quantitative Analysis. 2 vols. Translated by Cohn. 

Hillebrand, W. F. The Analysis of Silicate and Carbonate Rocks. 
Bulletin No. 305, United States Geological Survey. 

Ingle, H. Manual of Agricultural Chemistry. 

Journal of the Association of Official Agricultural Chemists. 

Leach, A. E. Food Inspection and Analysis (3d ed.). 

Leffman and Beam. Select Methods of Food Analysis. 

Lincoln and Walton. Elementary Quantitative Chemical Analysis. 

Mahin, E. G. Quantitative Analysis. 

Morse, H. N. Exercises in Quantitative Analysis. 

Olsen, J. C. Pure Foods. 

[82] 



Olsen, J. C. Quantitative Chemical Analysis (3d ed.). 

Richmond, II. D. Dairy Chemistry. 

Sherman, H. C. Organic Analysis (2d ed.). 

Snyder, H. Dairy Chemistry. 

Snyder, H. Soils and Fertilizers. 

Sutton, F. Volumetric Analysis (10th ed.). 

Talbot, H. P. Quantitative Chemical Analysis. 

Treadwell-Hall. Analytical Chemistry. Vol. II, Quantitative 

Analysis. 
Van Slyke, L. L. Modern Methods of testing Milk and, Milk 

Products. 1913. 
Wiley, H. W. Foods and their Adulteration. 1913. 
Wiley, H. W. Principles and Practice of Agricultural Analysis. 

Vol. I, "Soils" (1906); Vol. II, "Fertilizers and Insecticides" 

(1908); Vol. Ill, "Agricultural Products" (1911). 

TABLES OF WEIGHTS 
Metric System 

Milligram = 0.0154 grain 
Gram = 15.4323 grains 
Gram = 0.03527 ounce avoirdupois 
Gram = 0.0321 ounce troy 

Kilogram = 2.2046 pounds avoirdupois 

Kilogram = 2.6792 pounds troy 

Avoirdupois 

Long ton = 2240 pounds = 1016.047 kilograms 
Short ton = 2000 pounds = 907.184 kilograms 

Pound = 16 ounces = 7000 grains = 453.5924 grams 

Ounce = 437.5 grains = 28.3495 grams 
Grain = 64.798 milligrams = 0.06479 

Tro2j 

Pound = 12 ounces = 5760 grains = 373.241 grams 
Ounce = 20 pennyweights = 480 grains = 31.103 grams 
Pennyweight = 24 grains = 1.555 grams 

Grain =: 64.7989 milligrams = 0.06479 gram 

[83] 



Troy (^jjliarinacij) 

Ounce = 8 drams = 480 grains = 31.1034 grams 
Dram = 3 scruples = 60 grains = 3.8879 grams 
Scruple = 20 grains = 1.295 grams 

TABLES OF MEASURES 

Length 

Millimeter = 0.039 inch 
Centimeter = 0.393 inch 
Decimeter = 3.937 inches 
Meter = 39.37 inches 
Meter = 3.280 feet 
Meter = 1.0936 yards 
Inch = 2.540 centimeters 
Foot (12 inches) = 3.0480 decimeters 
Yard (3 feet) = 0.914 meter 
Mile (1760 yards) = 5280 feet 
Mile (1.609347 kilometers) = 1609.347 meters 

Surface 

Square millimeter = 0.00155 square inch 
Square centimeter = 0.1549 square inch 
Square decimeter = 15.499 square inches 
Square decimeter = 0.1076 square foot 

Square meter = 1549.997 square inches 
Square meter (10.764 square feet) = 1.195 square yards 

Volume 

Gallon (U.S.) = 231 cubic inches 
Gallon (U.S.) = 3.785 liters 
Quart (U.S.) = 0.946 liter 
Pint (U.S.) = 0.473 liter 
Liter (U.S.) = 2.113 pints (U.S.) 

= 1.0566 quarts (U.S.) 
= 0.264 gallon (U.S.) 
Cubic meter = 1.307 cubic yards 
= 35.314 cubic feet 
An imperial gallon (English) = 4.545 liters 

= 277.410 cubic inches (U.S.) 

[84] 



STRENGTH OF HCl SOLUTION AT DIFFERENT 
DENSITIES, 15°C. 



Specific 


Per cent 


Grams HCl 


Specific 


Per cent 


Grams HCl 


Gravity 


OF HCl 


IN 100 cc. 


Gravity 


OF HCl 


IN 100 cc. 


1.095 


19.06 


20.9 


1.150 


29.57 


34.0 


1.100 


20.01 


22.0 


1.155 


30.55 


35.3 


1.105 


20.97 


23.2 


1.160 


31.52 


36.6 


1.110 


21.92 


24.3 


1.165 


32.49 


37.9 


1.115 


22.86 


25.5 


1.170 


33.46 


39.2 


1.120 


23.82 


26.7 


1.175 


34.42 


40.4 


1.125 


24.78 


27.8 


1.180 


35.39 


41.8 


1.130 


25.75 


29.1 


1.185 


36.31 


43.0 


1.135 


26.70 


30.3 


1.190 


37.23 


44.3 


1.140 


27.66 


31.5 


1.195 


38.16 


45.6 


1.145 


28.61 


32.8 


1.200 


39.11 


46.9 



STRENGTH OF H2SO4 SOLUTION AT DIFFERENT 
DENSITIES, 15° C. 



Specific 
Gravity 


Per cent 

OF H2SO4 


Grams H2SO4 
IN 100 cc. 


Specific 
Gravity 


Per cent 

OF H2SO4 


Grams H2SO4 
IN 100 cc. 


1.700 


77.17 


131.2 


1.790 


85.70 


153.4 


1.710 


78.04 


133.4 


1.800 


86.90 


156.4 


1.720 


78.92 


135.7 


1.810 


88.30 


159.8 


1.730 


79.80 


138.1 


1.820 


90.02 


163.9 


1.740 


80.68 


140.4 


1.825 


91.00 


166.1 


1.750 


81.56 


142.7 


1.830 


92.10 


168.5 


1.760 


82.44 


145.1 


1.835 


93.43 


171.3 


1.770 


83.32 


147.5 


1.840 


95.60 


175.9 


1.780 


84.50 


150.4 









[85] 



STRENGTH OF HNO3 SOLUTION AT DIFFERENT 
DENSITIES, 15° C. 



Specific 
Gravity 


Per cent 

OF HNO3 


Grams HNO3 
IN 100 CO. 


Specific 
Gravity 


Per cent 

OF HNO3 


Grams HNO3 
IN 100 cc. 


1.20 


32.36 


38.8 


1.37 


59.39 


81.4 


1.21 


33.82 


40.9 


1.38 


61.27 


84.6 


1.22 


35.28 


43.0 


1.39 


63.23 


87.9 


1.23 


36.78 


45.2 


1.40 


65.30 


91.4 


1.24 


38.20 


47.5 


1.41 


67.50 


95.2 


1.25 


39.82 


49.8 


1.42 


69.80 


99.1 


1.26 


41.34 


52.1 


1.43 


72.17 


103.2 


1.27 


42.87 


54.4 


1.44 


74.68 


107.5 


1.28 


44.41 


56.8 


1.45 


77.28 


112.1 


1.29 


45.95 


69.3 


1.46 


79.98 


116.8 


1.30 


47.49 


61.7 


1.47 


82.90 


121.9 


1.31 


49.07 


64.3 


1.48 


86.05 


127.4 


1.32 


50.71 


66.0 


1.49 


89.60 


133.5 ^ 


1.33 


52.37 


69.7 


1.50 


94.09 


141.1 


1.34 


54.07 


72.5 


1.51 


98.10 


148.1 


1.35 


55.79 


75.3 


1.52 


99.67 


151.5 


1.36 


57.57 


78.3 









STRENGTH OF NH^OH SOLUTION AT DIFFERENT 
DENSITIES, 15° C. 



Specific 
Gravity 


Per cent 
of NH3 


Grams NH3 
IN 100 cc. 


Specific 
Gravity 


Per cent 

OF NH3 


Grams NH3 
IN 100 cc. " 


.936 


16.82 


15.74 


.916 


23.03 


21.09 


.934 


17.42 


16.27 


.914 


23.68 


21.63 


.932 


18.03 


16.81 


.912 


24.33 


22.19 


.930 


18.64 


17.34 


.910 


24.99 


22.74 


.928 


19.25 


17.86 


.908 


25.65 


23.29 


.926 


19.87 


18.42 


.906 


26.31 


23.83 


.924 


20.49 


18.93 


.904 


26.98 


24.39 


.922 


21.12 


19.47 


.902 


27.65 


24.94 


.920 


21.75 


20.01 


.900 


28.33 


25.50 


.918 


22.39 


20.56 


.898 


29.01 


26.05 



[86] 



STRENGTH OF NaOH SOLUTION AT DIFFERENT 
DENSITIES, 15° C. 



Specific Gravity 


Baume 


Per cent of NaOH 


Grams NaOH 
IX 100 cc. 


1.075 


10 


6.55 


7.0 


1.083 


11 


7.31 


7.9 


1.091 


12 


8.00 


8.7 


1.100 


13 


8.68 


9.5 


1.108 


14 


9.42 


10.4 


1.116 


15 


10.06 


11.2 


1.125 


16 


10.97 


12.3 


1.134 


17 


11.84 


13.4 


1.142 


18 


12.64 


14.4 


1.152 


19 


13.55 


15.6 


1.1G2 


20 


14.37 


16.7 


1.171 


21 


15.13 


17.7 


1.180 


22 


15.91 


18.8 


1.190 


23 


16.77 


20.0 


1.200 


24 


17.67 


21.2 


1.210 


25 


18.58 


22.5 


1.220 


26 


19.58 


23.9 


1.231 


27 


20.59 


25.3 


1.241 


28 


21.42 


26.6 


1.252 


29 


22.64 


28.3 


1.263 


30 


23.67 


29.9 


1.274 


31 


24.81 


31.6 


1.285 


32 


25.80 


33.2 


1.297 


33 


26.83 


34.8 


1.308 


34 


27.80 


36.4 


1.320 


35 


28.83 


38.1 


1.332 


36 


29.93 


39.9 


1.345 


37 


31.22 


42.0 


1.357 


38 


32.47 


44.1 


1.370 


39 


33.69 


46.2 


1.383 


40 


34.96 


48.3 


1.397 


41 


36.25 


50.6 


1.410 


42 


37.47 


52.8 


1.424 


43 


38.80 


55.3 


1.438 


44 


39.99 


57.5 


1.453 


45 


41.41 


60.2 



[87] 



SOLUBILITIES IN WATER 

All the chlorides are soluble except those of silver, lead, and 
mercurous mercuri/. 

All the sulphates are soluble except those of strontium, 
barium, and lead. 

All the carbonates and phosphates are insoluble except those 
of sodium,, potassium, and amvionium. 

All the hydroxides are insoluble except those of sodium, 
2)otassium, ammoniuMi, calcium, strontium, and barium. 

All nitrates, acetates, and chlorates are soluble. 

DIRECTIONS FOR PREPARATION OF REAGENTS 

Indicatoks for Volumetric Analysis 

Litmus. Boil 1 g. of purified powdered litmus with 60 cc. of 
distilled water, filter, and divide filtrate into two equal por- 
tions. To one portion add dilute H.^SO^, drop by drop, until 
the solution is just acid. Mix the two portions and keep in a 
glass-stoppered bottle. 

CochineaL Digest 1 g. of crushed cochineal dregs in 100 cc. 
of 25 per cent alcohol (be sure the alcohol is neutral) and filter. 

Methyl Orange. Dissolve 1/10 g. in 100 cc. of distilled water. 

Methyl Redo Dissolve 1/10 g. in 100 cc. of distilled water. 

Phenolphthalein. Dissolve 1 g. in 100 cc. of 50 per cent alcohol. 

Corallin. Saturate alcohol (that has previously been made 
neutral) with corallin. 

I. Solutions for Quantitative Analysis 

Asbestos for Gooch Crucible. Select a good grade of asbestos 
with long fibers. The asbestos should be separated until the 
fibers are about one-fourth inch long, then digested with con- 
centrated HCl for twelve hours, filtered, and washed with dis- 
tilled water until free from chlorides. Transfer the asbestos 
to a bottle containing distilled water 

[88] 



Silver Nitrate Solution. Dissolve 16.994 g. of silver nitrate 
(AgNOg) crystals in 1000 cc. of distilled water (free from 
chlorides) and place in a dark-colored bottle away from the 
sunlight. 

Ammonium Oxalate Solution. Dissolve 42 g. of ammonium 
oxalate ((NH2)2Cp^ • Hfi) in 1000 cc. of distilled water. 

11. Solutions used in the Analysis of Feedstuff 

Saturated Solution of Sodium Hydroxide. Dissolve about 
1000 g. of NaOH in 1 liter of water, cool, and pour into a 
bottle (crude NaOH may be used if the impurities are allowed 
to settle and the clear solution drawn off for use). 

Anhydrous, Alcohol-Free Ether. Let the ether stand in con- 
tact with calcium chloride (CaCl^, 50 g. to about 500 cc.) until 
next laboratory period, and distill, using a distilling tube. Place 
the distilled ether in a dry glass-stoppered bottle over metallic 
sodium free from" oil. For a short time leave the bottle loosely 
stoppered so that the hydrogen evolved may escape. The ether 
should be filtered, or the clear solution should be drawn off 
ivithout distui'hing the residue. 

III. Solutions used in the Anahjsis of Soils 

Ammonium Oxalate Solution. Prepared as in I. 

Sodium Ammonium Hydrogen Phosphate (Microcosmic Salt). 

Dissolve 100 g. of sodium ammonium hydrogen phosphate 
(NaNH^HPO^ . 4 Hp) in 1 liter of distilled water. 

Ammonium Molybdate Solution. "* Dissolve 100 g. of molybdic 
acid in 144 cc. of ammonium hydroxide (sp. gr. 0.90) and 
271 cc. of water ; slowly, and with constant stirring, pour the 
solution thus obtained into 489 cc. of nitric acid (sp. gr. 1.42) 
and 1148 cc. of water. Keep the mixture in a warm place for 

* Bulletin 107 (Revised), Bureau of Chemistry, United States Depart- 
ment of Agriculture. 

[89] 



several days or until a portion heated to 40*^ C. deposits no 
yellow precipitate of ammonium pliospliomolybdate. Decant 
the solution from any sediment and preserve in a glass-stoppered 
bottle. 

Ammonium Carbonate Solution. Add 250 cc. of ammonium hy- 
droxide (sp. gr. 0.90) to 250 g. ammonium carbonate ((NHJ^CO ) 
and make up to a liter. 

Saturated Solution of Sodium Hydroxide. Prepared as in I. 

Saturated Solution of Barium Hydroxide. Dissolve about 50 g. 
of barium hydroxide in 1 liter of water. 

Platinum Solution. Dissolve 172.8 g. PtCl^ in 1 liter of water. 
(1 cc. of the solution contains .1 g. of platinum, e(_[uivalent to 
.21 g. H^^PtCl^.) 

Solution of Oxalic Acid. Dissolve 3.2 g. of oxalic acid 
(Cfifi^ . 2H,0) in 500 cc. of distilled water containing 25 cc. 
of concentrated C. P. H.,SO^. Measure out, with a pipette or 
burette, two 25 cc. portions into beakers, add 2 cc. of H^SO^ 
(1 : 1), heat to 60° C, and titrate with the standard KMnO^ solu- 
tion. Note the volume of KMnO^ solution required to oxidize 
completely 1 cc. of the oxalic acid solution. 

Ammonium Chloride Solution saturated with Potassium Chloro- 
platinate. Dissolve 100 g. of ammonimn chloride in 500 cc. of 
water, add from 5 to 10 g. of pulverized potassium chloroplat- 
inate (potassium platinic chloride), and shake at intervals for 
six or eight hours. Allow tlie mixture to settle, filter, and use 
the clear filtrate for the potash determination. The residue 
may be used for the preparation of a fresh supply. 

Cobaltinitrite Reagent.* Dissolve 220 g. of sodium nitrite 
in 400 cc. of water and 113 g. of cobalt acetate in 300 cc. of 
water, and add 100 cc. of glacial acetic acid. The two solu- 
tions are mixed and gently warmed, NO2 is evolved, and the 
solution becomes dark colored. The NO^ is best evacuated from 
the bottle by a water pump and the liquid left overnight, 

* F. Sutton, Volumetric Analysis (Otb ed.), p. 62. 

[90] 



during whicli a yellow precipitate settles. The solution is 
then filtered and diluted with water to 1 liter. 

Alcohol Solution. Prepare the alcohol solution containing 
80 per cent alcohol (sp. gr. .8639 at 15° C). 

Asbestos for Gooch Crucible. Prepared as in I. 

IV. Solutions used in the Analysis of Fertilizers 

Ammonium Molybdate Solution. Prepared as in III. 

Ammonium Oxalate Solution. Prepared as in I. 

Ammonium Chloride Solution saturated with Potassium Chloro- 
platinate. Prepared as in III. 

Asbestos for Gooch Crucible. Prepared as in I. 

Alcohol Solution (8o%). Prepared as in III. 

Cobaltinitrite Reagent. Prepared as in III. 

Platinum Solution. Prepared as in III. 

Magnesia Mixture. Weigh out 11 g. of recently ignited cal- 
cined magnesia and dissolve in dilute hydrochloric acid, avoid- 
ing an excess. Add a little excess of magnesia and boil to 
precipitate iron, alumina, and phosphoric acid. Filter, add 
140 g. ammonium chloride and 130.5 g. of ammonium hydrox- 
ide (sp. gr. .9), and dilute to 1 liter. Instead of the calcined mag- 
nesia, 55 g. of crystallized magnesium chloride (MgCl^ • 6 H^O) 
may be used. 

Salicylic Acid Solution. Add 1 g. salicylic acid to 30 cc. 
H^SO^. Shake until thoroughly mixed, and allow it to stand 
from five to ten minutes, with frequent shakings. 

Ammonium Citrate Solution.* Dissolve 370 g. of commer- 
cial citric acid in 1500 cc. of water; nearly neutralize with 

* Hall, Journal of Industrial and Engineering Chemistry^ Vol. Ill (1911), 
p. 559 ; Rudnick, Journal of Industrial and Engineering Chemistry, Vol, V 
(1913), pp. 12, 998 ; E. D. Eastman and J. H. Hildebrand, Journal of 
Industrial and Engineering Chemistry, Vol. VI (1914), p. 578 ; Hall, Jour- 
nal of American Chemical Society, Yo\. XXXVII (January, 1915), p. 208. 
Bulletin 107 (Revised), Bureau of Chemistry, United States Department 
of Agriculture. 

[91] 



commercial ammonium hydroxide; cool; add ammonium hy- 
droxide until exactly neutral (testing with saturated alcoholic 
solution of corallin) ; and dilute to a volume of 2 liters. Deter- 
mine the specific gravity, which should be 1.09 at 20° C. 

V. Solutions used in the Amdysls of Insecticides 

Alcohol Solution (95% CgHgOH by Volume). Prepare a solu- 
tion of alcohol whose specific gravity is .8164 at 15° C. 

Potassium Ferrocyanide Solution. Dissolve 84 g, of potassium 
ferrocyanide (K^Fe(Cn)g) in 1 liter of distilled water. 

VI. Solutions used in the Analysis of Milk 

Anhydrous, Alcohol-Free Ether. Prepared as in II. 
Saturated Sodium Hydroxide Solution. Prepared as in II. 

VII. Soli(tio7is used in a Brief Sanitary Ejcaniination of Water 

Potassium Chromate Solution (Indicator). Dissolve 10 g. of 
potassium chromate (K^CrO^) in 100 cc. of distilled water. 

Nessler's Reagent.* Dissolve 62.5 g. of jootassium iodide in 
about 250 cc. of distilled water, set aside a few cubic centimeters, 
and add gradually to the larger part a cold saturated solution 
of mercuric chloride (of which about 500 cc. will be required) 
until the mercuric iodide precipitated ceases to redissolve on 
stirring. When a permanent precipitate is retained, restore 
the reserved potassium iodide so as to redissolve it, and con- 
tinue adding mercuric chloride very gradually until a slight 
precipitate remains undissolved. (The small quantity of j^otas- 
sium iodide is set aside merely to enable the mixture to be made 
rapidly without danger of adding an excess of mercury.) Next 
dissolve 150 g. of potassium hydroxide in 150 cc. distilled water, 
allow the solution to cool, add it gradually to the above solu- 
tion, and make up with distilled water to 1 liter. 

* F. Sutton, Vohunetric Analysis (10th ed.), p. 437. 

[92] 



On standing, a brown precipitate is deposited and the solu- 
tion becomes clear and of a pale greenish-yellow color. It is 
ready for use as soon as it is completely clear, and should 
be decanted into a smaller bottle as required. The reagent 
improves on keeping. 

Sulphanilic Solution. Dissolve .8 g. of the acid in 100 cc. of 
distilled water, heating if necessary. 

Naphthylamine Hydrochloride Solution. Dissolve .8 g. of the 
salt in 100 cc. of hot distilled water to which 1 cc. of llCl 
has been added. Filter through bone black, or add bone 
black to the solution, and decant as needed. Keep away from 
the light. 

Phenolsulphonic Acid. Mix 30 g. of phenol with 210 cc. or 
370 g. of concentrated H^SO^ in a flask. Place the flask in 
a water bath so that the surface of the liquid in the flask 
will be below the water. Heat for six hours at the temperature 
of boiling water. 



APPARATUS FOR DESK EQUIPMENT 



4 beakers: two 200 cc; two 350 cc. 
5 bottles : two 500 cc. ; two 1000 cc. ; 

one 250 cc. (wide-mouthed). 
2 Bunsen burners with 4 ft. of 

"rubber tubing, 
2 burettes, complete. 
1 burette holder. 
1 condenser with clamp. 

1 crucible tongs. 

2 crucibles, porcelain, No. 7, with 
covers. 

2 crucibles, Gooch. 

1 cylinder, graduated, 50 cc. 

1 desiccator, complete. 

2 evaporating dishes. No. 4. 
25 filter papers, 9 cm. 

1 flask, 500 cc. with rubber stop- 
per for wash bottle. 

4 flasks, Erlenmeyer : two 250 cc. ; 
two 500 cc. 

2 flasks, Kj eldahl digestion : 800 cc . 



2 flasks, measuring: one 250 cc; 

one 500 cc. 
1 flask, filtering. 

5 funnels: four 50mm.; one 
Gooch. 

1 funnel holder, wood. 
Matches, safety, 1 box. 

2 pipettes: one25cc; one 50cc. 
2 rings, iron, 3-inch. 

4 rods, glass. 
1 stand, iron. 

6 test tubes, 10 cm. 
1 test-tube brush. 

1 test-tube rack. 

1 thermometer, 100° C. 

Towel or one-half yard absorption 
cloth. 

2 triangles, pipestem. 
Tubing, glass, for wash bottle. 

4 watch glasses: one 35 mm.; one 
50 mm^ ; one 62 mm. ; one 80 mm. 



[93] 



INTERNATIONAL ATOMIC WEIGHTS (1916) 
Abridged Table 



Element 

Aluminium 
Antimony 
Arsenic . 
Barium . 
Bismuth . 
Boron 
Bromine . 
Calcium . 
Carbon . 
Chlorine . 
Chromium 
Cobalt . 
Copper . 
Fluorine 
Gold . . 
Hydrogen 
Iodine 
Iron . . 
Lead . . 



Symbol 

. Al 

. Sb 

. As 

. Ba 

. Bi 

. B 

. Br 

. Ca 

. C 

. CI 

. Cr 

. Co 

. Cu 

. F 

. Au 

. H 

. I 

. Fe 

. Pb 



AT03IIC! 

Weight 

27.10 

120.20 

74.96 

137.37 

208.00 

11.00 

79.92 

40.07 

12.00 

35.46 

52.00 

58.97 

63.57 

19.00 

197.20 

1.008 
126.92 
55.84 
207.20 



Element 



Symbol 



Lithium Li 

Magnesium .... Mg 

Manganese .... Mn 

Mercury Hg 

Molybdenum , , . Mo 

Nickel Ni 

Nitrogen N 

Oxygen 

Phosphorus . . . . P 

Platinum Pt 

Potassium . . . . K 

Silicon Si 

Silver Ag 

Sodium Na 

Strontium . . . , Sr 

Sulphur S 

Tin Sn 

Uranium U 

Zinc Zn 



Atomic 
Weight 

6.94 
24.32 
54.93 

200.6 
96.0 
58.68 
14.01 
16.0 
31.04 

195.2 
39.10 
28.30 

107.88 
23.00 
87.63 
32.06 

118.70 

238.20 
65.37 



[94] 



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